1. 7.2 APIs related to navigation and session history
      1. 7.2.1 Security infrastructure for Window, WindowProxy, and Location objects
        1. 7.2.1.1 Integration with IDL
        2. 7.2.1.2 Shared internal slot: [[CrossOriginPropertyDescriptorMap]]
        3. 7.2.1.3 Shared abstract operations
          1. 7.2.1.3.1 CrossOriginProperties ( O )
          2. 7.2.1.3.2 CrossOriginPropertyFallback ( P )
          3. 7.2.1.3.3 IsPlatformObjectSameOrigin ( O )
          4. 7.2.1.3.4 CrossOriginGetOwnPropertyHelper ( O, P )
          5. 7.2.1.3.5 CrossOriginGet ( O, P, Receiver )
          6. 7.2.1.3.6 CrossOriginSet ( O, P, V, Receiver )
          7. 7.2.1.3.7 CrossOriginOwnPropertyKeys ( O )
      2. 7.2.2 The Window object
        1. 7.2.2.1 Opening and closing windows
        2. 7.2.2.2 Indexed access on the Window object
        3. 7.2.2.3 Named access on the Window object
        4. 7.2.2.4 Accessing related windows
        5. 7.2.2.5 Historical browser interface element APIs
        6. 7.2.2.6 Script settings for Window objects
      3. 7.2.3 The WindowProxy exotic object
        1. 7.2.3.1 [[GetPrototypeOf]] ( )
        2. 7.2.3.2 [[SetPrototypeOf]] ( V )
        3. 7.2.3.3 [[IsExtensible]] ( )
        4. 7.2.3.4 [[PreventExtensions]] ( )
        5. 7.2.3.5 [[GetOwnProperty]] ( P )
        6. 7.2.3.6 [[DefineOwnProperty]] ( P, Desc )
        7. 7.2.3.7 [[Get]] ( P, Receiver )
        8. 7.2.3.8 [[Set]] ( P, V, Receiver )
        9. 7.2.3.9 [[Delete]] ( P )
        10. 7.2.3.10 [[OwnPropertyKeys]] ( )
      4. 7.2.4 The Location interface
        1. 7.2.4.1 [[GetPrototypeOf]] ( )
        2. 7.2.4.2 [[SetPrototypeOf]] ( V )
        3. 7.2.4.3 [[IsExtensible]] ( )
        4. 7.2.4.4 [[PreventExtensions]] ( )
        5. 7.2.4.5 [[GetOwnProperty]] ( P )
        6. 7.2.4.6 [[DefineOwnProperty]] ( P, Desc )
        7. 7.2.4.7 [[Get]] ( P, Receiver )
        8. 7.2.4.8 [[Set]] ( P, V, Receiver )
        9. 7.2.4.9 [[Delete]] ( P )
        10. 7.2.4.10 [[OwnPropertyKeys]] ( )
      5. 7.2.5 The History interface
      6. 7.2.6 Event interfaces
        1. 7.2.6.1 The PopStateEvent interface
        2. 7.2.6.2 The HashChangeEvent interface
        3. 7.2.6.3 The PageTransitionEvent interface
        4. 7.2.6.4 The BeforeUnloadEvent interface

7.2.1 Security infrastructure for Window, WindowProxy, and Location objects

Although typically objects cannot be accessed across origins, the web platform would not be true to itself if it did not have some legacy exceptions to that rule that the web depends upon.

This section uses the terminology and typographic conventions from the JavaScript specification. [JAVASCRIPT]

7.2.1.1 Integration with IDL

When perform a security check is invoked, with a platformObject, identifier, and type, run these steps:

  1. If platformObject is not a Window or Location object, then return.

  2. For each e of CrossOriginProperties(platformObject):

    1. If SameValue(e.[[Property]], identifier) is true, then:

      1. If type is "method" and e has neither [[NeedsGet]] nor [[NeedsSet]], then return.

      2. Otherwise, if type is "getter" and e.[[NeedsGet]] is true, then return.

      3. Otherwise, if type is "setter" and e.[[NeedsSet]] is true, then return.

  3. If IsPlatformObjectSameOrigin(platformObject) is false, then throw a "SecurityError" DOMException.

7.2.1.2 Shared internal slot: [[CrossOriginPropertyDescriptorMap]]

Window and Location objects both have a [[CrossOriginPropertyDescriptorMap]] internal slot, whose value is initially an empty map.

The [[CrossOriginPropertyDescriptorMap]] internal slot contains a map with entries whose keys are (currentGlobal, objectGlobal, propertyKey)-tuples and values are property descriptors, as a memoization of what is visible to scripts when currentGlobal inspects a Window or Location object from objectGlobal. It is filled lazily by CrossOriginGetOwnPropertyHelper, which consults it on future lookups.

User agents should allow a value held in the map to be garbage collected along with its corresponding key when nothing holds a reference to any part of the value. That is, as long as garbage collection is not observable.

For example, with const href = Object.getOwnPropertyDescriptor(crossOriginLocation, "href").set the value and its corresponding key in the map cannot be garbage collected as that would be observable.

User agents may have an optimization whereby they remove key-value pairs from the map when document.domain is set. This is not observable as document.domain cannot revisit an earlier value.

For example, setting document.domain to "example.com" on www.example.com means user agents can remove all key-value pairs from the map where part of the key is www.example.com, as that can never be part of the origin again and therefore the corresponding value could never be retrieved from the map.

7.2.1.3 Shared abstract operations
7.2.1.3.1 CrossOriginProperties ( O )
  1. Assert: O is a Location or Window object.

  2. If O is a Location object, then return « { [[Property]]: "href", [[NeedsGet]]: false, [[NeedsSet]]: true }, { [[Property]]: "replace" } ».

  3. Return « { [[Property]]: "window", [[NeedsGet]]: true, [[NeedsSet]]: false }, { [[Property]]: "self", [[NeedsGet]]: true, [[NeedsSet]]: false }, { [[Property]]: "location", [[NeedsGet]]: true, [[NeedsSet]]: true }, { [[Property]]: "close" }, { [[Property]]: "closed", [[NeedsGet]]: true, [[NeedsSet]]: false }, { [[Property]]: "focus" }, { [[Property]]: "blur" }, { [[Property]]: "frames", [[NeedsGet]]: true, [[NeedsSet]]: false }, { [[Property]]: "length", [[NeedsGet]]: true, [[NeedsSet]]: false }, { [[Property]]: "top", [[NeedsGet]]: true, [[NeedsSet]]: false }, { [[Property]]: "opener", [[NeedsGet]]: true, [[NeedsSet]]: false }, { [[Property]]: "parent", [[NeedsGet]]: true, [[NeedsSet]]: false }, { [[Property]]: "postMessage" } ».

This abstract operation does not return a Completion Record.

Indexed properties do not need to be safelisted in this algorithm, as they are handled directly by the WindowProxy object.

A JavaScript property name P is a cross-origin accessible window property name if it is "window", "self", "location", "close", "closed", "focus", "blur", "frames", "length", "top", "opener", "parent", "postMessage", or an array index property name.

7.2.1.3.2 CrossOriginPropertyFallback ( P )
  1. If P is "then", @@toStringTag, @@hasInstance, or @@isConcatSpreadable, then return PropertyDescriptor{ [[Value]]: undefined, [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: true }.

  2. Throw a "SecurityError" DOMException.

7.2.1.3.3 IsPlatformObjectSameOrigin ( O )
  1. Return true if the current settings object's origin is same origin-domain with O's relevant settings object's origin, and false otherwise.

This abstract operation does not return a Completion Record.

Here the current settings object roughly corresponds to the "caller", because this check occurs before the execution context for the getter/setter/method in question makes its way onto the JavaScript execution context stack. For example, in the code w.document, this step is invoked before the document getter is reached as part of the [[Get]] algorithm for the WindowProxy w.

7.2.1.3.4 CrossOriginGetOwnPropertyHelper ( O, P )

If this abstract operation returns undefined and there is no custom behavior, the caller needs to throw a "SecurityError" DOMException. In practice this is handled by the caller calling CrossOriginPropertyFallback.

  1. Let crossOriginKey be a tuple consisting of the current settings object, O's relevant settings object, and P.

  2. For each e of CrossOriginProperties(O):

    1. If SameValue(e.[[Property]], P) is true, then:

      1. If the value of the [[CrossOriginPropertyDescriptorMap]] internal slot of O contains an entry whose key is crossOriginKey, then return that entry's value.

      2. Let originalDesc be OrdinaryGetOwnProperty(O, P).

      3. Let crossOriginDesc be undefined.

      4. If e.[[NeedsGet]] and e.[[NeedsSet]] are absent, then:

        1. Let value be originalDesc.[[Value]].

        2. If IsCallable(value) is true, then set value to an anonymous built-in function, created in the current realm, that performs the same steps as the IDL operation P on object O.

        3. Set crossOriginDesc to PropertyDescriptor{ [[Value]]: value, [[Enumerable]]: false, [[Writable]]: false, [[Configurable]]: true }.

      5. Otherwise:

        1. Let crossOriginGet be undefined.

        2. If e.[[NeedsGet]] is true, then set crossOriginGet to an anonymous built-in function, created in the current realm, that performs the same steps as the getter of the IDL attribute P on object O.

        3. Let crossOriginSet be undefined.

        4. If e.[[NeedsSet]] is true, then set crossOriginSet to an anonymous built-in function, created in the current realm, that performs the same steps as the setter of the IDL attribute P on object O.

        5. Set crossOriginDesc to PropertyDescriptor{ [[Get]]: crossOriginGet, [[Set]]: crossOriginSet, [[Enumerable]]: false, [[Configurable]]: true }.

      6. Create an entry in the value of the [[CrossOriginPropertyDescriptorMap]] internal slot of O with key crossOriginKey and value crossOriginDesc.

      7. Return crossOriginDesc.

  3. Return undefined.

This abstract operation does not return a Completion Record.

The reason that the property descriptors produced here are configurable is to preserve the invariants of the essential internal methods required by the JavaScript specification. In particular, since the value of the property can change as a consequence of navigation, it is required that the property be configurable. (However, see tc39/ecma262 issue #672 and references to it elsewhere in this specification for cases where we are not able to preserve these invariants, for compatibility with existing web content.) [JAVASCRIPT]

The reason the property descriptors are non-enumerable, despite this mismatching the same-origin behavior, is for compatibility with existing web content. See issue #3183 for details.

7.2.1.3.5 CrossOriginGet ( O, P, Receiver )
  1. Let desc be ? O.[[GetOwnProperty]](P).

  2. Assert: desc is not undefined.

  3. If IsDataDescriptor(desc) is true, then return desc.[[Value]].

  4. Assert: IsAccessorDescriptor(desc) is true.

  5. Let getter be desc.[[Get]].

  6. If getter is undefined, then throw a "SecurityError" DOMException.

  7. Return ? Call(getter, Receiver).

7.2.1.3.6 CrossOriginSet ( O, P, V, Receiver )
  1. Let desc be ? O.[[GetOwnProperty]](P).

  2. Assert: desc is not undefined.

  3. If desc.[[Set]] is present and its value is not undefined, then:

    1. Perform ? Call(setter, Receiver, «V»).

    2. Return true.

  4. Throw a "SecurityError" DOMException.

7.2.1.3.7 CrossOriginOwnPropertyKeys ( O )
  1. Let keys be a new empty List.

  2. For each e of CrossOriginProperties(O), append e.[[Property]] to keys.

  3. Return the concatenation of keys and « "then", @@toStringTag, @@hasInstance, @@isConcatSpreadable ».

This abstract operation does not return a Completion Record.

7.2.2 The Window object

Window

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android37+Samsung Internet?Opera Android10.1+
[Global=Window,
 Exposed=Window,
 LegacyUnenumerableNamedProperties]
interface Window : EventTarget {
  // the current browsing context
  [LegacyUnforgeable] readonly attribute WindowProxy window;
  [Replaceable] readonly attribute WindowProxy self;
  [LegacyUnforgeable] readonly attribute Document document;
  attribute DOMString name; 
  [PutForwards=href, LegacyUnforgeable] readonly attribute Location location;
  readonly attribute History history;
  readonly attribute CustomElementRegistry customElements;
  [Replaceable] readonly attribute BarProp locationbar;
  [Replaceable] readonly attribute BarProp menubar;
  [Replaceable] readonly attribute BarProp personalbar;
  [Replaceable] readonly attribute BarProp scrollbars;
  [Replaceable] readonly attribute BarProp statusbar;
  [Replaceable] readonly attribute BarProp toolbar;
  attribute DOMString status;
  undefined close();
  readonly attribute boolean closed;
  undefined stop();
  undefined focus();
  undefined blur();

  // other browsing contexts
  [Replaceable] readonly attribute WindowProxy frames;
  [Replaceable] readonly attribute unsigned long length;
  [LegacyUnforgeable] readonly attribute WindowProxy? top;
  attribute any opener;
  [Replaceable] readonly attribute WindowProxy? parent;
  readonly attribute Element? frameElement;
  WindowProxy? open(optional USVString url = "", optional DOMString target = "_blank", optional [LegacyNullToEmptyString] DOMString features = "");
  getter object (DOMString name);
  // Since this is the global object, the IDL named getter adds a NamedPropertiesObject exotic
  // object on the prototype chain. Indeed, this does not make the global object an exotic object.
  // Indexed access is taken care of by the WindowProxy exotic object.

  // the user agent
  readonly attribute Navigator navigator;
  readonly attribute Navigator clientInformation; // legacy alias of .navigator
  readonly attribute boolean originAgentCluster;

  // user prompts
  undefined alert();
  undefined alert(DOMString message);
  boolean confirm(optional DOMString message = "");
  DOMString? prompt(optional DOMString message = "", optional DOMString default = "");
  undefined print();

  undefined postMessage(any message, USVString targetOrigin, optional sequence<object> transfer = []);
  undefined postMessage(any message, optional WindowPostMessageOptions options = {});

  // also has obsolete members
};
Window includes GlobalEventHandlers;
Window includes WindowEventHandlers;

dictionary WindowPostMessageOptions : StructuredSerializeOptions {
  USVString targetOrigin = "/";
};
window.window

Window/window

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+
window.frames

Window/frames

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+
window.self

Window/self

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

These attributes all return window.

window.document

Window/document

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the Document associated with window.

document.defaultView

Document/defaultView

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer9+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the Window associated with document, if there is one, or null otherwise.

The Window object has an associated Document, which is a Document object. It is set when the Window object is created, and only ever changed during navigation from the initial about:blank Document.

A Window's browsing context is its associated Document's browsing context. It is either null or a browsing context.

A Window's navigable is the navigable whose active document is the Window's associated Document's, or null if there is no such navigable.

The window, frames, and self getter steps are to return this's relevant realm.[[GlobalEnv]].[[GlobalThisValue]].

The document getter steps are to return this's associated Document.

The Document object associated with a Window object can change in exactly one case: when the navigate algorithm creates a new Document object for the first page loaded in a browsing context. In that specific case, the Window object of the initial about:blank page is reused and gets a new Document object.

The defaultView getter steps are:

  1. If this's browsing context is null, then return null.

  2. Return this's browsing context's WindowProxy object.


HTMLDocument

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

For historical reasons, Window objects must also have a writable, configurable, non-enumerable property named HTMLDocument whose value is the Document interface object.

7.2.2.1 Opening and closing windows
window = window.open([ url [, target [, features ] ] ])

Window/open

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Opens a window to show url (defaults to "about:blank"), and returns it. target (defaults to "_blank") gives the name of the new window. If a window already exists with that name, it is reused. The features argument can contain a set of comma-separated tokens:

"noopener"
"noreferrer"

These behave equivalently to the noopener and noreferrer link types on hyperlinks.

"popup"

Encourages user agents to provide a minimal web browser user interface for the new window. (Impacts the visible getter on all BarProp objects as well.)

globalThis.open("https://email.example/message/CAOOOkFcWW97r8yg=SsWg7GgCmp4suVX9o85y8BvNRqMjuc5PXg", undefined, "noopener,popup");
window.name [ = value ]

Window/name

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the name of the window.

Can be set, to change the name.

window.close()

Window/close

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Closes the window.

window.closed

Window/closed

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns true if the window has been closed, false otherwise.

window.stop()

Window/stop

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)14+Internet ExplorerNo
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Cancels the document load.

The window open steps, given a string url, a string target, and a string features, are as follows:

  1. If the event loop's termination nesting level is nonzero, return null.

  2. Let sourceDocument be the entry global object's associated Document.

  3. If target is the empty string, then set target to "_blank".

  4. Let tokenizedFeatures be the result of tokenizing features.

  5. Let noopener and noreferrer be false.

  6. If tokenizedFeatures["noopener"] exists, then:

    1. Set noopener to the result of parsing tokenizedFeatures["noopener"] as a boolean feature.

    2. Remove tokenizedFeatures["noopener"].

  7. If tokenizedFeatures["noreferrer"] exists, then:

    1. Set noreferrer to the result of parsing tokenizedFeatures["noreferrer"] as a boolean feature.

    2. Remove tokenizedFeatures["noreferrer"].

  8. Let referrerPolicy be the empty string.

  9. If noreferrer is true, then set noopener to true and set referrerPolicy to "no-referrer".

  10. Let targetNavigable and windowType be the result of applying the rules for choosing a navigable given target, sourceDocument's node navigable, and noopener.

    If there is a user agent that supports control-clicking a link to open it in a new tab, and the user control-clicks on an element whose onclick handler uses the window.open() API to open a page in an iframe element, the user agent could override the selection of the target browsing context to instead target a new tab.

  11. If targetNavigable is null, then return null.

  12. If windowType is either "new and unrestricted" or "new with no opener", then:

    1. Set targetNavigable's active browsing context's is popup to the result of checking if a popup window is requested, given tokenizedFeatures.

    2. Set up browsing context features for targetNavigable's active browsing context given tokenizedFeatures.[CSSOMVIEW]

    3. Let urlRecord be the URL record about:blank.

    4. If url is not the empty string, then parse url relative to the entry settings object, and set urlRecord to the resulting URL record, if any. If the parse a URL algorithm failed, then throw a "SyntaxError" DOMException.

    5. If urlRecord matches about:blank, then perform the URL and history update steps given targetNavigable's active document and urlRecord.

      This is necessary in case url is something like about:blank?foo. If url is just plain about:blank, this will do nothing.

    6. Otherwise, navigate targetNavigable to urlRecord using sourceDocument, with referrerPolicy set to referrerPolicy and exceptionsEnabled set to true.

  13. Otherwise:

    1. If url is not the empty string, then:

      1. Let urlRecord be the URL record about:blank.

      2. Parse url relative to the entry settings object, and set urlRecord to the resulting URL record, if any. If the parse a URL algorithm failed, then throw a "SyntaxError" DOMException.

      3. Navigate targetNavigable to urlRecord using sourceDocument, with referrerPolicy set to referrerPolicy and exceptionsEnabled set to true.

    2. If noopener is false, then set targetNavigable's active browsing context's opener browsing context to sourceDocument's browsing context.

  14. If noopener is true or windowType is "new with no opener", then return null.

  15. Return targetNavigable's active WindowProxy.

The open(url, target, features) method steps are to run the window open steps with url, target, and features.

The method provides a mechanism for navigating an existing browsing context or opening and navigating an auxiliary browsing context.


To tokenize the features argument:

  1. Let tokenizedFeatures be a new ordered map.

  2. Let position point at the first code point of features.

  3. While position is not past the end of features:

    1. Let name be the empty string.

    2. Let value be the empty string.

    3. Collect a sequence of code points that are feature separators from features given position. This skips past leading separators before the name.

    4. Collect a sequence of code points that are not feature separators from features given position. Set name to the collected characters, converted to ASCII lowercase.

    5. Set name to the result of normalizing the feature name name.

    6. While position is not past the end of features and the code point at position in features is not U+003D (=):

      1. If the code point at position in features is U+002C (,), or if it is not a feature separator, then break.

      2. Advance position by 1.

      This skips to the first U+003D (=) but does not skip past a U+002C (,) or a non-separator.

    7. If the code point at position in features is a feature separator:

      1. While position is not past the end of features and the code point at position in features is a feature separator:

        1. If the code point at position in features is U+002C (,), then break.

        2. Advance position by 1.

        This skips to the first non-separator but does not skip past a U+002C (,).

      2. Collect a sequence of code points that are not feature separators code points from features given position. Set value to the collected code points, converted to ASCII lowercase.

    8. If name is not the empty string, then set tokenizedFeatures[name] to value.

  4. Return tokenizedFeatures.

To check if a window feature is set, given tokenizedFeatures, featureName, and defaultValue:

  1. If tokenizedFeatures[featureName] exists, then return the result of parsing tokenizedFeatures[featureName] as a boolean feature.

  2. Return defaultValue.

To check if a popup window is requested, given tokenizedFeatures:

  1. If tokenizedFeatures is empty, then return false.

  2. If tokenizedFeatures["popup"] exists, then return the result of parsing tokenizedFeatures["popup"] as a boolean feature.

  3. Let location be the result of checking if a window feature is set, given tokenizedFeatures, "location", and false.

  4. Let toolbar be the result of checking if a window feature is set, given tokenizedFeatures, "toolbar", and false.

  5. If location and toolbar are both false, then return true.

  6. Let menubar be the result of checking if a window feature is set, given tokenizedFeatures, menubar", and false.

  7. If menubar is false, then return true.

  8. Let resizable be the result of checking if a window feature is set, given tokenizedFeatures, "resizable", and true.

  9. If resizable is false, then return true.

  10. Let scrollbars be the result of checking if a window feature is set, given tokenizedFeatures, "scrollbars", and false.

  11. If scrollbars is false, then return true.

  12. Let status be the result of checking if a window feature is set, given tokenizedFeatures, "status", and false.

  13. If status is false, then return true.

  14. Return false.

A code point is a feature separator if it is ASCII whitespace, U+003D (=), or U+002C (,).

For legacy reasons, there are some aliases of some feature names. To normalize a feature name name, switch on name:

"screenx"
Return "left".
"screeny"
Return "top".
"innerwidth"
Return "width".
"innerheight"
Return "height".
Anything else
Return name.

To parse a boolean feature given a string value:

  1. If value is the empty string, then return true.

  2. If value is "yes", then return true.

  3. If value is "true", then return true.

  4. Let parsed be the result of parsing value as an integer.

  5. If parsed is an error, then set it to 0.

  6. Return false if parsed is 0, and true otherwise.


The name getter steps are:

  1. If this's navigable is null, then return the empty string.

  2. Return this's navigable's target name.

The name setter steps are:

  1. If this's navigable is null, then return.

  2. Set this's navigable's active session history entry's document state's navigable target name to the given value.

The name gets reset when the navigable is navigated to another origin.


The close() method steps are:

  1. Let thisTraversable be null.

  2. For each top-level traversable traversable of the user agent's top-level traversable set: if traversable's active document's relevant global object equals this, then set thisTraversable to traversable and break.

  3. If thisTraversable is null, then return.

    In this case the method is being called on a Window that does not correspond to a top-level traversable, and so closing is not allowed.

  4. If thisTraversable's is closing is true, then return.

  5. Let browsingContext be thisTraversable's active browsing context.

  6. Let sourceSnapshotParams be the result of snapshotting source snapshot params given thisTraversable's active document.

  7. If all the following are true:

    then:

    1. Set thisTraversable's is closing to true.

    2. Queue a task on the DOM manipulation task source to close thisTraversable.

A navigable is script-closable if its active browsing context is an auxiliary browsing context that was created by a script (as opposed to by an action of the user), or if it is a top-level traversable whose session history entries's size is 1.

The closed getter steps are to return true if this's browsing context is null or its is closing is true; otherwise false.

The stop() method steps are:

  1. If this's navigable is null, then return.

  2. Stop loading this's navigable.

7.2.2.2 Indexed access on the Window object
window.length

Window/length

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the number of document-tree child navigables.

window[index]

Returns the WindowProxy corresponding to the indicated document-tree child navigables.

The length getter steps are to return this's associated Document's document-tree child navigables's size.

Indexed access to document-tree child navigables is defined through the [[GetOwnProperty]] internal method of the WindowProxy object.

7.2.2.3 Named access on the Window object
window[name]

Returns the indicated element or collection of elements.

As a general rule, relying on this will lead to brittle code. Which IDs end up mapping to this API can vary over time, as new features are added to the web platform, for example. Instead of this, use document.getElementById() or document.querySelector().

The document-tree child navigable target name property set of a Window object window is the return value of running these steps:

  1. Let children be the document-tree child navigables of window's associated Document.

  2. Let firstNamedChildren be an empty ordered set.

  3. For each navigable of children:

    1. Let name be navigable's target name.

    2. If name is the empty string, then continue.

    3. If names contains name, then continue.

    4. Append navigable to firstNamedChildren.

  4. Let names be an empty ordered set.

  5. For each navigable of firstNamedChildren:

    1. Let name be navigable's target name.

    2. If navigable's active document's origin is same origin with window's relevant settings object's origin, then append name to names.

  6. Return names.

The two seperate iterations mean that in the following example, hosted on https://example.org/, assuming https://elsewhere.example/ sets window.name to "spices", evaluating window.spices after everything has loaded will yield undefined:

<iframe src=https://elsewhere.example.com/></iframe>
<iframe name=spices></iframe>

The Window object supports named properties. The supported property names of a Window object window at any moment consist of the following, in tree order according to the element that contributed them, ignoring later duplicates:

To determine the value of a named property name in a Window object window, the user agent must return the value obtained using the following steps:

  1. Let objects be the list of named objects of window with the name name.

    There will be at least one such object, by definition.

  2. If objects contains a navigable, then:

    1. Let container be the first navigable container in window's associated Document's descendants whose nested navigable is in objects.

    2. Return container's nested navigable's active WindowProxy.

  3. Otherwise, if objects has only one element, return that element.

  4. Otherwise return an HTMLCollection rooted at window's associated Document, whose filter matches only named objects of window with the name name. (By definition, these will all be elements.)

Named objects of Window object window with the name name, for the purposes of the above algorithm, consist of the following:

window.top

Window/top

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android4+Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the WindowProxy for the top-level traversable.

window.opener [ = value ]

Window/opener

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer9+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Returns the WindowProxy for the opener browsing context.

Returns null if there isn't one or if it has been set to null.

Can be set to null.

window.parent

Window/parent

Support in all current engines.

Firefox1+Safari1.3+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer9+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Returns the WindowProxy for the parent navigable.

window.frameElement

Window/frameElement

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer5.5+
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the navigable container element.

Returns null if there isn't one, and in cross-origin situations.

The top getter steps are:

  1. If this's navigable is null, then return null.

  2. Return this's navigable's top-level traversable's active WindowProxy.

The opener getter steps are:

  1. Let current be this's browsing context.

  2. If current is null, then return null.

  3. If current's disowned is true, then return null.

  4. If current's opener browsing context is null, then return null.

  5. Return current's opener browsing context's WindowProxy object.

The opener setter steps are:

  1. If the given value is null and this's browsing context is non-null, then set this's browsing context's disowned to true.

  2. If the given value is non-null, then return ? OrdinaryDefineOwnProperty(this, "opener", { [[Value]]: the given value, [[Writable]]: true, [[Enumerable]]: true, [[Configurable]]: true }).

If a browsing context's disowned is true, its window.opener attribute is null. That prevents scripts in the browsing context from changing any properties of its opener browsing context's Window object (i.e., the Window object from which the browsing context was created).

Otherwise, if a browsing context's disowned is false, then scripts in that browsing context can use window.opener to change properties of its opener browsing context's Window object. For example, a script running in the browsing context can change the value of window.opener.location, causing the opener browsing context to navigate to a completely different document.

The parent getter steps are:

  1. Let navigable be this's navigable.

  2. If navigable is null, then return null.

  3. If navigable's parent is not null, then set navigable to navigable's parent.

  4. Return navigable's active WindowProxy.

The frameElement getter steps are:

  1. Let current be this's node navigable.

  2. If current is null, then return null.

  3. Let container be current's container.

  4. If container is null, then return null.

  5. If container's node document's origin is not same origin-domain with the current settings object's origin, then return null.

  6. Return container.

An example of when these properties can return null is as follows:

<!DOCTYPE html>
<iframe></iframe>

<script>
"use strict";
const element = document.querySelector("iframe");
const iframeWindow = element.contentWindow;
element.remove();

console.assert(iframeWindow.top === null);
console.assert(iframeWindow.parent === null);
console.assert(iframeWindow.frameElement === null);
</script>

Here the browsing context corresponding to iframeWindow was nulled out when element was removed from the document.

7.2.2.5 Historical browser interface element APIs

For historical reasons, the Window interface had some properties that represented the visibility of certain web browser interface elements.

For privacy and interoperability reasons, those properties now return values that represent whether the Window's browsing context's is popup property is true or false.

Each interface element is represented by a BarProp object:

BarProp

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera?Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS1+Chrome Android?WebView Android37+Samsung Internet?Opera Android?
[Exposed=Window]
interface BarProp {
  readonly attribute boolean visible;
};
window.locationbar.visible

Window/locationbar

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera?Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android?
window.menubar.visible

Window/menubar

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera?Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android?
window.personalbar.visible

Window/personalbar

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+
window.scrollbars.visible

Window/scrollbars

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+
window.statusbar.visible

Window/statusbar

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera?Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android?
window.toolbar.visible

Window/toolbar

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera?Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android?

Returns true if the Window is not a popup; otherwise, returns false.

BarProp/visible

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera?Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS1+Chrome Android?WebView Android37+Samsung Internet?Opera Android?

The visible getter steps are:

  1. Let browsingContext be this's relevant global object's browsing context.

  2. If browsingContext is null, then return true.

  3. Return the negation of browsingContext's top-level browsing context's is popup.

The following BarProp objects must exist for each Window object:

The location bar BarProp object
Historically represented the user interface element that contains a control that displays the browser's location bar.
The menu bar BarProp object
Historically represented the user interface element that contains a list of commands in menu form, or some similar interface concept.
The personal bar BarProp object
Historically represented the user interface element that contains links to the user's favorite pages, or some similar interface concept.
The scrollbar BarProp object
Historically represented the user interface element that contains a scrolling mechanism, or some similar interface concept.
The status bar BarProp object
Historically represented a user interface element found immediately below or after the document, as appropriate for the user's media, which typically provides information about ongoing network activity or information about elements that the user's pointing device is currently indicating.
The toolbar BarProp object
Historically represented the user interface element found immediately above or before the document, as appropriate for the user's media, which typically provides session history traversal controls (back and forward buttons, reload buttons, etc.).

The locationbar attribute must return the location bar BarProp object.

The menubar attribute must return the menu bar BarProp object.

The personalbar attribute must return the personal bar BarProp object.

The scrollbars attribute must return the scrollbar BarProp object.

The statusbar attribute must return the status bar BarProp object.

The toolbar attribute must return the toolbar BarProp object.


For historical reasons, the status attribute on the Window object must, on getting, return the last string it was set to, and on setting, must set itself to the new value. When the Window object is created, the attribute must be set to the empty string. It does not do anything else.

7.2.2.6 Script settings for Window objects

To set up a window environment settings object, given a URL creationURL, a JavaScript execution context execution context, null or an environment reservedEnvironment, a URL topLevelCreationURL, and an origin topLevelOrigin, run these steps:

  1. Let realm be the value of execution context's Realm component.

  2. Let window be realm's global object.

  3. Let settings object be a new environment settings object whose algorithms are defined as follows:

    The realm execution context

    Return execution context.

    The module map

    Return the module map of window's associated Document.

    The API URL character encoding

    Return the current character encoding of window's associated Document.

    The API base URL

    Return the current base URL of window's associated Document.

    The origin

    Return the origin of window's associated Document.

    The policy container

    Return the policy container of window's associated Document.

    The cross-origin isolated capability

    Return true if both of the following hold, and false otherwise:

    1. realm's agent cluster's cross-origin-isolation mode is "concrete", and

    2. window's associated Document is allowed to use the "cross-origin-isolated" feature.

    The time origin

    Return window's associated Document's load timing info's navigation start time.

  4. If reservedEnvironment is non-null, then:

    1. Set settings object's id to reservedEnvironment's id, target browsing context to reservedEnvironment's target browsing context, and active service worker to reservedEnvironment's active service worker.

    2. Set reservedEnvironment's id to the empty string.

      The identity of the reserved environment is considered to be fully transferred to the created environment settings object. The reserved environment is not searchable by the environment’s id from this point on.

  5. Otherwise, set settings object's id to a new unique opaque string, settings object's target browsing context to null, and settings object's active service worker to null.

  6. Set settings object's creation URL to creationURL, settings object's top-level creation URL to topLevelCreationURL, and settings object's top-level origin to topLevelOrigin.

  7. Set realm's [[HostDefined]] field to settings object.

7.2.3 The WindowProxy exotic object

A WindowProxy is an exotic object that wraps a Window ordinary object, indirecting most operations through to the wrapped object. Each browsing context has an associated WindowProxy object. When the browsing context is navigated, the Window object wrapped by the browsing context's associated WindowProxy object is changed.

The WindowProxy exotic object must use the ordinary internal methods except where it is explicitly specified otherwise below.

There is no WindowProxy interface object.

Every WindowProxy object has a [[Window]] internal slot representing the wrapped Window object.

Although WindowProxy is named as a "proxy", it does not do polymorphic dispatch on its target's internal methods as a real proxy would, due to a desire to reuse machinery between WindowProxy and Location objects. As long as the Window object remains an ordinary object this is unobservable and can be implemented either way.

7.2.3.1 [[GetPrototypeOf]] ( )
  1. Let W be the value of the [[Window]] internal slot of this.

  2. If IsPlatformObjectSameOrigin(W) is true, then return ! OrdinaryGetPrototypeOf(W).

  3. Return null.

7.2.3.2 [[SetPrototypeOf]] ( V )
  1. Return ! SetImmutablePrototype(this, V).

7.2.3.3 [[IsExtensible]] ( )
  1. Return true.

7.2.3.4 [[PreventExtensions]] ( )
  1. Return false.

7.2.3.5 [[GetOwnProperty]] ( P )
  1. Let W be the value of the [[Window]] internal slot of this.

  2. If P is an array index property name, then:

    1. Let index be ! ToUint32(P).

    2. Let children be the document-tree child navigables of W's associated Document.

    3. Let value be undefined.

    4. If index is less than children's size, then:

      1. Sort children in ascending order, with navigableA being less than navigableB if navigableA's container was inserted into W's associated Document earlier than navigableB's container was.

      2. Set value to children[index]'s active WindowProxy.

    5. If value is undefined, then:

      1. If IsPlatformObjectSameOrigin(W) is true, then return undefined.

      2. Throw a "SecurityError" DOMException.

    6. Return PropertyDescriptor{ [[Value]]: value, [[Writable]]: false, [[Enumerable]]: true, [[Configurable]]: true }.

  3. If IsPlatformObjectSameOrigin(W) is true, then return ! OrdinaryGetOwnProperty(W, P).

    This is a willful violation of the JavaScript specification's invariants of the essential internal methods to maintain compatibility with existing web content. See tc39/ecma262 issue #672 for more information. [JAVASCRIPT]

  4. Let property be CrossOriginGetOwnPropertyHelper(W, P).

  5. If property is not undefined, then return property.

  6. If property is undefined and P is in W's document-tree child navigable target name property set, then:

    1. Let value be the active WindowProxy of the named object of W with the name P.

    2. Return PropertyDescriptor{ [[Value]]: value, [[Enumerable]]: false, [[Writable]]: false, [[Configurable]]: true }.

      The reason the property descriptors are non-enumerable, despite this mismatching the same-origin behavior, is for compatibility with existing web content. See issue #3183 for details.

  7. Return ? CrossOriginPropertyFallback(P).

7.2.3.6 [[DefineOwnProperty]] ( P, Desc )
  1. Let W be the value of the [[Window]] internal slot of this.

  2. If IsPlatformObjectSameOrigin(W) is true, then:

    1. If P is an array index property name, return false.

    2. Return ? OrdinaryDefineOwnProperty(W, P, Desc).

      This is a willful violation of the JavaScript specification's invariants of the essential internal methods to maintain compatibility with existing web content. See tc39/ecma262 issue #672 for more information. [JAVASCRIPT]

  3. Throw a "SecurityError" DOMException.

7.2.3.7 [[Get]] ( P, Receiver )
  1. Let W be the value of the [[Window]] internal slot of this.

  2. Check if an access between two browsing contexts should be reported, given the current global object's browsing context, W's browsing context, P, and the current settings object.

  3. If IsPlatformObjectSameOrigin(W) is true, then return ? OrdinaryGet(this, P, Receiver).

  4. Return ? CrossOriginGet(this, P, Receiver).

this is passed rather than W as OrdinaryGet and CrossOriginGet will invoke the [[GetOwnProperty]] internal method.

7.2.3.8 [[Set]] ( P, V, Receiver )
  1. Let W be the value of the [[Window]] internal slot of this.

  2. Check if an access between two browsing contexts should be reported, given the current global object's browsing context, W's browsing context, P, and the current settings object.

  3. If IsPlatformObjectSameOrigin(W) is true, then:

    1. If P is an array index property name, then return false.

    2. Return ? OrdinarySet(W, P, V, Receiver).

  4. Return ? CrossOriginSet(this, P, V, Receiver).

    this is passed rather than W as CrossOriginSet will invoke the [[GetOwnProperty]] internal method.

7.2.3.9 [[Delete]] ( P )
  1. Let W be the value of the [[Window]] internal slot of this.

  2. If IsPlatformObjectSameOrigin(W) is true, then:

    1. If P is an array index property name, then:

      1. Let desc be ! this.[[GetOwnProperty]](P).

      2. If desc is undefined, then return true.

      3. Return false.

    2. Return ? OrdinaryDelete(W, P).

  3. Throw a "SecurityError" DOMException.

7.2.3.10 [[OwnPropertyKeys]] ( )
  1. Let W be the value of the [[Window]] internal slot of this.

  2. Let maxProperties be W's associated Document's document-tree child navigables's size.

  3. Let keys be the range 0 to maxProperties, exclusive.

  4. If IsPlatformObjectSameOrigin(W) is true, then return the concatenation of keys and OrdinaryOwnPropertyKeys(W).

  5. Return the concatenation of keys and ! CrossOriginOwnPropertyKeys(W).

7.2.4 The Location interface

Document/location

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Location

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer3+
Firefox Android?Safari iOS?Chrome Android?WebView Android37+Samsung Internet?Opera Android10.1+

Window/location

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Each Window object is associated with a unique instance of a Location object, allocated when the Window object is created.

The Location exotic object is defined through a mishmash of IDL, invocation of JavaScript internal methods post-creation, and overridden JavaScript internal methods. Coupled with its scary security policy, please take extra care while implementing this excrescence.

To create a Location object, run these steps:

  1. Let location be a new Location platform object.

  2. Let valueOf be location's relevant realm.[[Intrinsics]].[[%Object.prototype.valueOf%]].

  3. Perform ! location.[[DefineOwnProperty]]("valueOf", { [[Value]]: valueOf, [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }).

  4. Perform ! location.[[DefineOwnProperty]](@@toPrimitive, { [[Value]]: undefined, [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }).

  5. Set the value of the [[DefaultProperties]] internal slot of location to location.[[OwnPropertyKeys]]().

  6. Return location.

The addition of valueOf and @@toPrimitive own data properties, as well as the fact that all of Location's IDL attributes are marked [LegacyUnforgeable], is required by legacy code that consulted the Location interface, or stringified it, to determine the document URL, and then used it in a security-sensitive way. In particular, the valueOf, @@toPrimitive, and [LegacyUnforgeable] stringifier mitigations ensure that code such as foo[location] = bar or location + "" cannot be misdirected.

document.location [ = value ]
window.location [ = value ]

Returns a Location object with the current page's location.

Can be set, to navigate to another page.

The Document object's location getter steps are to return this's relevant global object's Location object, if this is fully active, and null otherwise.

The Window object's location getter steps are to return this's Location object.

Location objects provide a representation of the URL of their associated Document, as well as methods for navigating and reloading the associated navigable.

[Exposed=Window]
interface Location { // but see also additional creation steps and overridden internal methods
  [LegacyUnforgeable] stringifier attribute USVString href;
  [LegacyUnforgeable] readonly attribute USVString origin;
  [LegacyUnforgeable] attribute USVString protocol;
  [LegacyUnforgeable] attribute USVString host;
  [LegacyUnforgeable] attribute USVString hostname;
  [LegacyUnforgeable] attribute USVString port;
  [LegacyUnforgeable] attribute USVString pathname;
  [LegacyUnforgeable] attribute USVString search;
  [LegacyUnforgeable] attribute USVString hash;

  [LegacyUnforgeable] undefined assign(USVString url);
  [LegacyUnforgeable] undefined replace(USVString url);
  [LegacyUnforgeable] undefined reload();

  [LegacyUnforgeable, SameObject] readonly attribute DOMStringList ancestorOrigins;
};
location.toString()
location.href

Location/href

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer3+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Location/toString

Support in all current engines.

Firefox22+Safari1+Chrome52+
Opera?Edge79+
Edge (Legacy)12+Internet Explorer11
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android?

Returns the Location object's URL.

Can be set, to navigate to the given URL.

location.origin

Location/origin

Support in all current engines.

Firefox21+Safari5.1+Chrome8+
Opera?Edge79+
Edge (Legacy)12+Internet Explorer11
Firefox Android?Safari iOS?Chrome Android?WebView Android3+Samsung Internet?Opera Android?

Returns the Location object's URL's origin.

location.protocol

Location/protocol

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer3+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the Location object's URL's scheme.

Can be set, to navigate to the same URL with a changed scheme.

location.host

Location/host

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer3+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the Location object's URL's host and port (if different from the default port for the scheme).

Can be set, to navigate to the same URL with a changed host and port.

location.hostname

Location/hostname

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer3+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the Location object's URL's host.

Can be set, to navigate to the same URL with a changed host.

location.port

Location/port

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer3+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the Location object's URL's port.

Can be set, to navigate to the same URL with a changed port.

location.pathname

Location/pathname

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer3+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the Location object's URL's path.

Can be set, to navigate to the same URL with a changed path.

location.search

Location/search

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer3+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the Location object's URL's query (includes leading "?" if non-empty).

Can be set, to navigate to the same URL with a changed query (ignores leading "?").

location.hash

Location/hash

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer3+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the Location object's URL's fragment (includes leading "#" if non-empty).

Can be set, to navigate to the same URL with a changed fragment (ignores leading "#").

location.assign(url)

Location/assign

Support in all current engines.

Firefox1+Safari3+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer5.5+
Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Navigates to the given URL.

location.replace(url)

Location/replace

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer5.5+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Removes the current page from the session history and navigates to the given URL.

location.reload()

Location/reload

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer5.5+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Reloads the current page.

location.ancestorOrigins

Location/ancestorOrigins

FirefoxNoSafari6+Chrome20+
Opera?Edge79+
Edge (Legacy)?Internet ExplorerNo
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android?

Returns a DOMStringList object listing the origins of the ancestor navigables' active documents.

A Location object has an associated relevant Document, which is its relevant global object's browsing context's active document, if this Location object's relevant global object's browsing context is non-null, and null otherwise.

A Location object has an associated url, which is this Location object's relevant Document's URL, if this Location object's relevant Document is non-null, and about:blank otherwise.

A Location object has an associated ancestor origins list. When a Location object is created, its ancestor origins list must be set to a DOMStringList object whose associated list is the list of strings that the following steps would produce:

  1. Let output be a new list of strings.

  2. Let current be the Location object's relevant Document.

  3. While current's container document is non-null:

    1. Set current to current's container document.

    2. Append the serialization of current's origin to output.

  4. Return output.

To Location-object navigate a Location object location to a URL url, optionally given a history handling behavior historyHandling (default "push"):

  1. Let navigable be location's relevant global object's navigable.

  2. Let sourceDocument be the incumbent global object's associated Document.

  3. If location's relevant Document is not yet completely loaded, and the incumbent global object does not have transient activation, then set historyHandling to "replace".

  4. Navigate navigable to url using sourceDocument, with exceptionsEnabled set to true and historyHandling set to historyHandling.

The href getter steps are:

  1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  2. Return this's url, serialized.

The href setter steps are:

  1. If this's relevant Document is null, then return.

  2. Parse the given value relative to the entry settings object. If that failed, throw a "SyntaxError" DOMException.

  3. Location-object navigate this to the resulting URL record.

The href setter intentionally has no security check.

The origin getter steps are:

  1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  2. Return the serialization of this's url's origin.

The protocol getter steps are:

  1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  2. Return this's url's scheme, followed by ":".

The protocol setter steps are:

  1. If this's relevant Document is null, then return.

  2. If this's relevant Document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  3. Let copyURL be a copy of this's url.

  4. Let possibleFailure be the result of basic URL parsing the given value, followed by ":", with copyURL as url and scheme start state as state override.

    Because the URL parser ignores multiple consecutive colons, providing a value of "https:" (or even "https::::") is the same as providing a value of "https".

  5. If possibleFailure is failure, then throw a "SyntaxError" DOMException.

  6. If copyURL's scheme is not an HTTP(S) scheme, then terminate these steps.

  7. Location-object navigate this to copyURL.

The host getter steps are:

  1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  2. Let url be this's url.

  3. If url's host is null, return the empty string.

  4. If url's port is null, return url's host, serialized.

  5. Return url's host, serialized, followed by ":" and url's port, serialized.

The host setter steps are:

  1. If this's relevant Document is null, then return.

  2. If this's relevant Document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  3. Let copyURL be a copy of this's url.

  4. If copyURL has an opaque path, then return.

  5. Basic URL parse the given value, with copyURL as url and host state as state override.

  6. Location-object navigate this to copyURL.

The hostname getter steps are:

  1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  2. If this's url's host is null, return the empty string.

  3. Return this's url's host, serialized.

The hostname setter steps are:

  1. If this's relevant Document is null, then return.

  2. If this's relevant Document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  3. Let copyURL be a copy of this's url.

  4. If copyURL has an opaque path, then return.

  5. Basic URL parse the given value, with copyURL as url and hostname state as state override.

  6. Location-object navigate this to copyURL.

The port getter steps are:

  1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  2. If this's url's port is null, return the empty string.

  3. Return this's url's port, serialized.

The port setter steps are:

  1. If this's relevant Document is null, then return.

  2. If this's relevant Document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  3. Let copyURL be a copy of this's url.

  4. If copyURL cannot have a username/password/port, then return.

  5. If the given value is the empty string, then set copyURL's port to null.

  6. Otherwise, basic URL parse the given value, with copyURL as url and port state as state override.

  7. Location-object navigate this to copyURL.

The pathname getter steps are:

  1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  2. Return the result of URL path serializing this Location object's url.

The pathname setter steps are:

  1. If this's relevant Document is null, then return.

  2. If this's relevant Document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  3. Let copyURL be a copy of this's url.

  4. If copyURL has an opaque path, then return.

  5. Set copyURL's path to the empty list.

  6. Basic URL parse the given value, with copyURL as url and path start state as state override.

  7. Location-object navigate this to copyURL.

The search getter steps are:

  1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  2. If this's url's query is either null or the empty string, return the empty string.

  3. Return "?", followed by this's url's query.

The search setter steps are:

  1. If this's relevant Document is null, then return.

  2. If this's relevant Document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  3. Let copyURL be a copy of this's url.

  4. If the given value is the empty string, set copyURL's query to null.

  5. Otherwise, run these substeps:

    1. Let input be the given value with a single leading "?" removed, if any.

    2. Set copyURL's query to the empty string.

    3. Basic URL parse input, with null, the relevant Document's document's character encoding, copyURL as url, and query state as state override.

  6. Location-object navigate this to copyURL.

The hash getter steps are:

  1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  2. If this's url's fragment is either null or the empty string, return the empty string.

  3. Return "#", followed by this's url's fragment.

The hash setter steps are:

  1. If this's relevant Document is null, then return.

  2. If this's relevant Document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  3. Let copyURL be a copy of this's url.

  4. Let input be the given value with a single leading "#" removed, if any.

  5. Set copyURL's fragment to the empty string.

  6. Basic URL parse input, with copyURL as url and fragment state as state override.

  7. If copyURL's fragment is this's url's fragment, then return.

    This bailout is necessary for compatibility with deployed content, which redundantly sets location.hash on scroll. It does not apply to other mechanisms of fragment navigation, such as the location.href setter or location.assign().

  8. Location-object navigate this to copyURL.

Unlike the equivalent API for the a and area elements, the hash setter does not special case the empty string, to remain compatible with deployed scripts.


The assign(url) method steps are:

  1. If this's relevant Document is null, then return.

  2. If this's relevant Document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  3. Parse url relative to the entry settings object. If that failed, throw a "SyntaxError" DOMException.

  4. Location-object navigate this to the resulting URL record.

The replace(url) method steps are:

  1. If this's relevant Document is null, then return.

  2. Parse url relative to the entry settings object. If that failed, throw a "SyntaxError" DOMException.

  3. Location-object navigate this to the resulting URL record given "replace".

The replace() method intentionally has no security check.

The reload() method steps are:

  1. Let document be this's relevant Document.

  2. If document is null, then return.

  3. If document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  4. Reload document's node navigable.


The ancestorOrigins getter steps are:

  1. If this's relevant Document is null, then return an empty list.

  2. If this's relevant Document's origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.

  3. Otherwise, return this's ancestor origins list.

The details of how the ancestorOrigins attribute works are still controversial and might change. See issue #1918 for more information.


As explained earlier, the Location exotic object requires additional logic beyond IDL for security purposes. The Location object must use the ordinary internal methods except where it is explicitly specified otherwise below.

Also, every Location object has a [[DefaultProperties]] internal slot representing its own properties at time of its creation.

7.2.4.1 [[GetPrototypeOf]] ( )
  1. If IsPlatformObjectSameOrigin(this) is true, then return ! OrdinaryGetPrototypeOf(this).

  2. Return null.

7.2.4.2 [[SetPrototypeOf]] ( V )
  1. Return ! SetImmutablePrototype(this, V).

7.2.4.3 [[IsExtensible]] ( )
  1. Return true.

7.2.4.4 [[PreventExtensions]] ( )
  1. Return false.

7.2.4.5 [[GetOwnProperty]] ( P )
  1. If IsPlatformObjectSameOrigin(this) is true, then:

    1. Let desc be OrdinaryGetOwnProperty(this, P).

    2. If the value of the [[DefaultProperties]] internal slot of this contains P, then set desc.[[Configurable]] to true.

    3. Return desc.

  2. Let property be CrossOriginGetOwnPropertyHelper(this, P).

  3. If property is not undefined, then return property.

  4. Return ? CrossOriginPropertyFallback(P).

7.2.4.6 [[DefineOwnProperty]] ( P, Desc )
  1. If IsPlatformObjectSameOrigin(this) is true, then:

    1. If the value of the [[DefaultProperties]] internal slot of this contains P, then return false.

    2. Return ? OrdinaryDefineOwnProperty(this, P, Desc).

  2. Throw a "SecurityError" DOMException.

7.2.4.7 [[Get]] ( P, Receiver )
  1. If IsPlatformObjectSameOrigin(this) is true, then return ? OrdinaryGet(this, P, Receiver).

  2. Return ? CrossOriginGet(this, P, Receiver).

7.2.4.8 [[Set]] ( P, V, Receiver )
  1. If IsPlatformObjectSameOrigin(this) is true, then return ? OrdinarySet(this, P, V, Receiver).

  2. Return ? CrossOriginSet(this, P, V, Receiver).

7.2.4.9 [[Delete]] ( P )
  1. If IsPlatformObjectSameOrigin(this) is true, then return ? OrdinaryDelete(this, P).

  2. Throw a "SecurityError" DOMException.

7.2.4.10 [[OwnPropertyKeys]] ( )
  1. If IsPlatformObjectSameOrigin(this) is true, then return OrdinaryOwnPropertyKeys(this).

  2. Return CrossOriginOwnPropertyKeys(this).

7.2.5 The History interface

History

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer10+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Window/history

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera3+Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+
enum ScrollRestoration { "auto", "manual" };

[Exposed=Window]
interface History {
  readonly attribute unsigned long length;
  attribute ScrollRestoration scrollRestoration;
  readonly attribute any state;
  undefined go(optional long delta = 0);
  undefined back();
  undefined forward();
  undefined pushState(any data, DOMString unused, optional USVString? url = null);
  undefined replaceState(any data, DOMString unused, optional USVString? url = null);
};
history.length

History/length

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer10+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the number of overall session history entries for the current traversable navigable.

history.scrollRestoration

History/scrollRestoration

Support in all current engines.

Firefox46+Safari11+Chrome46+
Opera?Edge79+
Edge (Legacy)?Internet ExplorerNo
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android?

Returns the scroll restoration mode of the active session history entry.

history.scrollRestoration = value

Set the scroll restoration mode of the active session history entry to value.

history.state

History/state

Support in all current engines.

Firefox4+Safari6+Chrome19+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer10+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the serialized state of the active session history entry, deserialized into a JavaScript value.

history.go()

Reloads the current page.

history.go(delta)

History/go

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer10+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Goes back or forward the specified number of steps in the overall session history entries list for the current traversable navigable.

A zero delta will reload the current page.

If the delta is out of range, does nothing.

history.back()

History/back

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer10+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Goes back one step in the overall session history entries list for the current traversable navigable.

If there is no previous page, does nothing.

history.forward()

History/forward

Support in all current engines.

Firefox1+Safari1+Chrome1+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer10+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Goes forward one step in the overall session history entries list for the current traversable navigable.

If there is no next page, does nothing.

history.pushState(data, "")

History/pushState

Support in all current engines.

Firefox4+Safari5+Chrome5+
Opera11.5+Edge79+
Edge (Legacy)12+Internet Explorer10+
Firefox Android?Safari iOS4+Chrome Android?WebView Android37+Samsung Internet?Opera Android11.5+

Adds a new entry into session history with its serialized state set to a serialization of data. The active history entry's URL will be copied over and used for the new entry's URL.

(The second parameter exists for historical reasons, and cannot be omitted; passing the empty string is traditional.)

history.pushState(data, "", url)

Adds a new entry into session history with its serialized state set to a serialization of data, and with its URL set to url.

If the current Document cannot have its URL rewritten to url, a "SecurityError" DOMException will be thrown.

(The second parameter exists for historical reasons, and cannot be omitted; passing the empty string is traditional.)

history.replaceState(data, "")

History/replaceState

Support in all current engines.

Firefox4+Safari5+Chrome5+
Opera11.5+Edge79+
Edge (Legacy)12+Internet Explorer10+
Firefox Android?Safari iOS4+Chrome Android?WebView Android37+Samsung Internet?Opera Android11.5+

Updates the serialized state of the active session history entry to a structured clone of data.

(The second parameter exists for historical reasons, and cannot be omitted; passing the empty string is traditional.)

history.replaceState(data, "", url)

Updates the serialized state of the active session history entry to a structured clone of data, and its URL to url.

If the current Document cannot have its URL rewritten to url, a "SecurityError" DOMException will be thrown.

(The second parameter exists for historical reasons, and cannot be omitted; passing the empty string is traditional.)

A Document has a history object, a History object.

The history getter steps are to return this's associated Document's history object.


Each History object has state, initially null.

Each History object has a length, a non-negative integer, initially 0.

Each History object has an index, a non-negative integer, initially 0.

Although the index is not directly exposed, it can be inferred from changes to the length during synchronous navigations. In fact, that is what it's used for.

The length getter steps are:

  1. If this's relevant global object's associated Document is not fully active, then throw a "SecurityError" DOMException.

  2. Return this's length.

The scrollRestoration getter steps are:

  1. If this's relevant global object's associated Document is not fully active, then throw a "SecurityError" DOMException.

  2. Return this's node navigable's active session history entry's scroll restoration mode.

The scrollRestoration setter steps are:

  1. If this's relevant global object's associated Document is not fully active, then throw a "SecurityError" DOMException.

  2. Set this's node navigable's active session history entry's scroll restoration mode to the given value.

The state getter steps are:

  1. If this's relevant global object's associated Document is not fully active, then throw a "SecurityError" DOMException.

  2. Return this's state.

The go(delta) method steps are to delta traverse this given delta.

The back() method steps are to delta traverse this given −1.

The forward() method steps are to delta traverse this given +1.

To delta traverse a History object history given an integer delta:

  1. Let document be history's relevant global object's associated Document.

  2. If document is not fully active, then throw a "SecurityError" DOMException.

  3. If delta is 0, then reload document's node navigable.

  4. Traverse the history by a delta given document's node navigable's traversable navigable, delta, and document.

The pushState(data, unused, url) method steps are to run the shared history push/replace state steps given this, data, url, and "push".

The replaceState(data, unused, url) method steps are to run the shared history push/replace state steps given this, data, url, and "replace".

The shared history push/replace state steps, given a History history, a value data, a scalar value string-or-null url, and a history handling behavior historyHandling, are:

  1. Let document be history's associated Document.

  2. If document is not fully active, then throw a "SecurityError" DOMException.

  3. Optionally, return. (For example, the user agent might disallow calls to these methods that are invoked on a timer, or from event listeners that are not triggered in response to a clear user action, or that are invoked in rapid succession.)

  4. Let serializedData be StructuredSerializeForStorage(data). Rethrow any exceptions.

  5. Let newURL be document's URL.

  6. If url is not null, then:

    1. Parse url, relative to the relevant settings object of history.

    2. If that fails, then throw a "SecurityError" DOMException.

    3. Set newURL to the resulting URL record.

    4. If document cannot have its URL rewritten to newURL, then throw a "SecurityError" DOMException.

  7. Run the URL and history update steps given document and newURL, with serializedData set to serializedData and historyHandling set to historyHandling.

User agents may limit the number of state objects added to the session history per page. If a page hits the implementation-defined limit, user agents must remove the entry immediately after the first entry for that Document object in the session history after having added the new entry. (Thus the state history acts as a FIFO buffer for eviction, but as a LIFO buffer for navigation.)

A Document document can have its URL rewritten to a URL targetURL if the following algorithm returns true:

  1. Let documentURL be document's URL.

  2. If targetURL and documentURL differ in their scheme, username, password, host, or port components, then return false.

  3. If targetURL's scheme is an HTTP(S) scheme, then return true. (Differences in path, query, and fragment are allowed for http: and https: URLs.)

  4. If targetURL's scheme is "file", and targetURL and documentURL differ in their path component, then return false. (Differences in query and fragment are allowed for file: URLs.)

  5. If targetURL and documentURL differ in their path component or query components, then return false. (Only differences in fragment are allowed for other types of URLs.)

  6. Return true.

document's URL targetURL can have its URL rewritten
https://example.com/home https://example.com/home#about
https://example.com/home https://example.com/home?page=shop
https://example.com/home https://example.com/shop
https://example.com/home https://user:pass@example.com/home
https://example.com/home http://example.com/home
file:///path/to/x file:///path/to/x#hash
file:///path/to/x file:///path/to/x?search
file:///path/to/x file:///path/to/y
about:blank about:blank#hash
about:blank about:blank?search
about:blank about:srcdoc
data:text/html,foo data:text/html,foo#hash
data:text/html,foo data:text/html,foo?search
data:text/html,foo data:text/html,bar
data:text/html,foo data:bar
blob:https://example.com/77becafe-657b-4fdc-8bd3-e83aaa5e8f43 blob:https://example.com/77becafe-657b-4fdc-8bd3-e83aaa5e8f43#hash
blob:https://example.com/77becafe-657b-4fdc-8bd3-e83aaa5e8f43 blob:https://example.com/77becafe-657b-4fdc-8bd3-e83aaa5e8f43?search
blob:https://example.com/77becafe-657b-4fdc-8bd3-e83aaa5e8f43 blob:https://example.com/anything
blob:https://example.com/77becafe-657b-4fdc-8bd3-e83aaa5e8f43 blob:path

Note how only the URL of the Document matters, and not its origin. They can mismatch in cases like about:blank Documents with inherited origins, in sandboxed iframes, or when the document.domain setter has been used.

Consider a game where the user can navigate along a line, such that the user is always at some coordinate, and such that the user can bookmark the page corresponding to a particular coordinate, to return to it later.

A static page implementing the x=5 position in such a game could look like the following:

<!DOCTYPE HTML>
<!-- this is https://example.com/line?x=5 -->
<html lang="en">
<title>Line Game - 5</title>
<p>You are at coordinate 5 on the line.</p>
<p>
 <a href="?x=6">Advance to 6</a> or
 <a href="?x=4">retreat to 4</a>?
</p>

The problem with such a system is that each time the user clicks, the whole page has to be reloaded. Here instead is another way of doing it, using script:

<!DOCTYPE HTML>
<!-- this starts off as https://example.com/line?x=5 -->
<html lang="en">
<title>Line Game - 5</title>
<p>You are at coordinate <span id="coord">5</span> on the line.</p>
<p>
 <a href="?x=6" onclick="go(1); return false;">Advance to 6</a> or
 <a href="?x=4" onclick="go(-1); return false;">retreat to 4</a>?
</p>
<script>
 var currentPage = 5; // prefilled by server
 function go(d) {
   setupPage(currentPage + d);
   history.pushState(currentPage, "", '?x=' + currentPage);
 }
 onpopstate = function(event) {
   setupPage(event.state);
 }
 function setupPage(page) {
   currentPage = page;
   document.title = 'Line Game - ' + currentPage;
   document.getElementById('coord').textContent = currentPage;
   document.links[0].href = '?x=' + (currentPage+1);
   document.links[0].textContent = 'Advance to ' + (currentPage+1);
   document.links[1].href = '?x=' + (currentPage-1);
   document.links[1].textContent = 'retreat to ' + (currentPage-1);
 }
</script>

In systems without script, this still works like the previous example. However, users that do have script support can now navigate much faster, since there is no network access for the same experience. Furthermore, contrary to the experience the user would have with just a naïve script-based approach, bookmarking and navigating the session history still work.

In the example above, the data argument to the pushState() method is the same information as would be sent to the server, but in a more convenient form, so that the script doesn't have to parse the URL each time the user navigates.

Most applications want to use the same scroll restoration mode value for all of their history entries. To achieve this they can set the scrollRestoration attribute as soon as possible (e.g., in the first script element in the document's head element) to ensure that any entry added to the history session gets the desired scroll restoration mode.

<head>
  <script>
       if ('scrollRestoration' in history)
            history.scrollRestoration = 'manual';
  </script>
</head>
   
7.2.6.1 The PopStateEvent interface

PopStateEvent

Support in all current engines.

Firefox4+Safari6+Chrome4+
Opera12.1+Edge79+
Edge (Legacy)12+Internet Explorer10+
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+
[Exposed=Window]
interface PopStateEvent : Event {
  constructor(DOMString type, optional PopStateEventInit eventInitDict = {});

  readonly attribute any state;
};

dictionary PopStateEventInit : EventInit {
  any state = null;
};
event.state

Returns a copy of the information that was provided to pushState() or replaceState().

The state attribute must return the value it was initialized to. It represents the context information for the event, or null, if the state represented is the initial state of the Document.

7.2.6.2 The HashChangeEvent interface

HashChangeEvent

Support in all current engines.

Firefox3.6+Safari5+Chrome8+
Opera10.6+Edge79+
Edge (Legacy)12+Internet Explorer8+
Firefox Android?Safari iOS5+Chrome Android?WebView Android?Samsung Internet?Opera Android11+
[Exposed=Window]
interface HashChangeEvent : Event {
  constructor(DOMString type, optional HashChangeEventInit eventInitDict = {});

  readonly attribute USVString oldURL;
  readonly attribute USVString newURL;
};

dictionary HashChangeEventInit : EventInit {
  USVString oldURL = "";
  USVString newURL = "";
};
event.oldURL

HashChangeEvent/oldURL

Support in all current engines.

Firefox6+Safari5.1+Chrome8+
Opera12.1+Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the URL of the session history entry that was previously current.

event.newURL

HashChangeEvent/newURL

Support in all current engines.

Firefox6+Safari5.1+Chrome8+
Opera12.1+Edge79+
Edge (Legacy)12+Internet ExplorerNo
Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the URL of the session history entry that is now current.

The oldURL attribute must return the value it was initialized to. It represents context information for the event, specifically the URL of the session history entry that was traversed from.

The newURL attribute must return the value it was initialized to. It represents context information for the event, specifically the URL of the session history entry that was traversed to.

7.2.6.3 The PageTransitionEvent interface

PageTransitionEvent

Support in all current engines.

Firefox1.5+Safari5+Chrome4+
Opera?Edge79+
Edge (Legacy)12+Internet Explorer11
Firefox Android?Safari iOS4+Chrome Android?WebView Android37+Samsung Internet?Opera Android?
[Exposed=Window]
interface PageTransitionEvent : Event {
  constructor(DOMString type, optional PageTransitionEventInit eventInitDict = {});

  readonly attribute boolean persisted;
};

dictionary PageTransitionEventInit : EventInit {
  boolean persisted = false;
};
event.persisted

PageTransitionEvent/persisted

Support in all current engines.

Firefox11+Safari5+Chrome4+
Opera?Edge79+
Edge (Legacy)12+Internet Explorer11
Firefox Android?Safari iOS4+Chrome Android?WebView Android37+Samsung Internet?Opera Android?

For the pageshow event, returns false if the page is newly being loaded (and the load event will fire). Otherwise, returns true.

For the pagehide event, returns false if the page is going away for the last time. Otherwise, returns true, meaning that the page might be reused if the user navigates back to this page (if the Document's salvageable state stays true).

Things that can cause the page to be unsalvageable include:

The persisted attribute must return the value it was initialized to. It represents the context information for the event.

To fire a page transition event named eventName at a Window window with a boolean persisted, fire an event named eventName at window, using PageTransitionEvent, with the persisted attribute initialized to persisted, the cancelable attribute initialized to true, the bubbles attribute initialized to true, and legacy target override flag set.

The values for cancelable and bubbles don't make any sense, since canceling the event does nothing and it's not possible to bubble past the Window object. They are set to true for historical reasons.

7.2.6.4 The BeforeUnloadEvent interface

BeforeUnloadEvent

Support in all current engines.

Firefox1.5+Safari7+Chrome30+
Opera?Edge79+
Edge (Legacy)12+Internet Explorer4+
Firefox Android?Safari iOS?Chrome Android?WebView Android37+Samsung Internet3.0+Opera Android?
[Exposed=Window]
interface BeforeUnloadEvent : Event {
  attribute DOMString returnValue;
};

There are no BeforeUnloadEvent-specific initialization methods.

The BeforeUnloadEvent interface is a legacy interface which allows checking if unloading is user-canceled to be controlled not only by canceling the event, but by setting the returnValue attribute to a value besides the empty string. Authors should use the preventDefault() method, or other means of canceling events, instead of using returnValue.

The returnValue attribute controls the process of checking if unloading is user-canceled. When the event is created, the attribute must be set to the empty string. On getting, it must return the last value it was set to. On setting, the attribute must be set to the new value.

This attribute is a DOMString only for historical reasons. Any value besides the empty string will be treated as a request to ask the user for confirmation.