HTML: The Living Standard

Edition for Web Developers — Last Updated 10 October 2022

1. 1. 7.9 Browsing the web
      1. 7.9.1 History traversal
         1. 7.9.1.1 The PopStateEvent interface
         2. 7.9.1.2 The HashChangeEvent interface
         3. 7.9.1.3 The PageTransitionEvent interface
      2. 7.9.2 Unloading documents
         1. 7.9.2.1 The BeforeUnloadEvent interface
      3. 7.9.3 The `X-Frame-Options` header
      4. 7.9.4 The `Refresh` header

7.9 Browsing the web

7.9.1 History traversal

7.9.1.1 The PopStateEvent interface

event.state

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

7.9.1.2 The HashChangeEvent interface

event.oldURL

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

event.newURL

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

7.9.1.3 The PageTransitionEvent interface

event.persisted

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 user agent decided to not keep the Document alive in a session history entry after unload
• Having iframes that are not salvageable
• Active WebSocket objects
• Aborting a Document

7.9.2 Unloading documents

7.9.2.1 The BeforeUnloadEvent interface

There are no BeforeUnloadEvent-specific initialization methods.

The BeforeUnloadEvent interface is a legacy interface which allows prompting to unload 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.

7.9.3 The `X-Frame-Options` header

The `X-Frame-Options` HTTP response header is a legacy way of controlling whether and how a Document may be loaded inside of a child browsing context. It is obsoleted by the frame-ancestors CSP directive, which provides more granular control over the same situations. It was originally defined in HTTP Header Field X-Frame-Options, but the definition here supersedes that document. [CSP] [RFC7034]

In particular, HTTP Header Field X-Frame-Options specified an `ALLOW-FROM` variant of the header, but that is not to be implemented.

If both a CSP frame-ancestors directive and an `X-Frame-Options` header are used in the same response, then `X-Frame-Options` is ignored.

For web developers and conformance checkers, its value ABNF is:

X-Frame-Options = "DENY" / "SAMEORIGIN"

7.9.4 The `Refresh` header

The `Refresh` HTTP response header is the HTTP-equivalent to a meta element with an http-equiv attribute in the Refresh state. It takes the same value and works largely the same. Its processing model is detailed in create and initialize a Document object.