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JavaScript and History Navigation

Traditionally, Opera has used fast history navigation, when navigating back and forward through history. This means that pages are preserved in the exact state that they were in when you left the page, and are able to display faster. Occasionally, some pages rely on scripts being able to detect when you load and unload pages using scripts, but these cannot detect fast history navigation.

Starting in Opera 9.0 Technical Preview 2, Opera attempts to detect pages that rely on this behavior, and will not use fast history navigation on those pages. This means that the page, and any scripts it contains, will be loaded from cache, and processed again when the page is loaded using the back or forward navigation. This is known as "compatible history navigation". An example of where this might be used is when an onload script changes parts of other pages in a frameset.

As well as automatically selecting an appropriate history navigation mode, Opera allows you to specify what history navigation mode you want it to use, using any of these three techniques:

These are specified in order of decreasing priority, so if a Web page sets the navigation mode to "compatible", and an opera:config setting sets it to "fast", then Opera will use fast history navigation. By default, Opera will use its automatic setting. If any of these three methods are set to automatic, Opera will use the next one instead.

User JavaScript

User JavaScripts can call the opera.setOverrideHistoryNavigationMode method, passing it one of these values: 'automatic', 'compatible', or 'fast'.

A setting available in opera:config

The [User Prefs] History Navigation Mode setting can be set to 1 (sets automatic mode), 2 (sets compatible mode), or 3 (sets fast mode).

Web page scripts

Scripts can set the history.navigationMode property to one of these values: 'automatic', 'compatible', or 'fast'.

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