Session Restore

In Firefox 2 and above, a built-in Session Store feature saves your session data, including open windows and tabs, window size and position, and text typed in forms. Session data is stored in the sessionstore.js file, located in the profile folder. To disable this feature, set the preference browser.sessionstore.enabled to false (see Editing configuration).

Default behavior

Firefox will automatically restore your session after an automatic update, or when using the restart button from the Add-ons Manager. Firefox will offer to restore your session after a crash or other unexpected close.

Starting in Firefox 3.5, Firefox automatically restores your session after one crash. If it crashes again, Firefox displays an error page offering to restore the previous session or start a new session. [1]

Always restore sessions on start

By default this feature is off, but can be turned on from the Options/Preferences menu. In the Main panel, under Startup set "When Firefox starts" to "Show my windows and tabs from last time". This will have Firefox restore your tabs and form data to their state when Firefox closed (the related preference is browser.startup.page).

If you want Firefox to restore multiple windows you need to close Firefox via "File -> Exit" ("Firefox -> Quit Firefox" on Mac OS). Closing the windows one at a time will cause Firefox to only restore the last window that was closed.

Restoring a session once

Set browser.sessionstore.resume_session_once to "true" in about:config and it will restore your session the next time you start Firefox, but not again.

Firefox keeps crashing after restoring a session

If a site's content caused your crash (e.g. a plugin is crashing) restoring your session may restore that page and cause Firefox to crash again. If Firefox keeps crashing after choosing "Restore Session," choose "Start New Session."

Starting in Firefox 3.5, your previous session is automatically restored after one crash, with no error page displayed. To change this behavior, modify the preference browser.sessionstore.max_resumed_crashes (default is 1). Set this preference to 0 if you do not want Firefox to automatically restore your session after a crash. [2]

Disable

To disable the crash recovery feature, set browser.sessionstore.resume_from_crash to false:

• Type about:config in the Location Bar
• Press Enter
• Find browser.sessionstore.resume_from_crash
• Double click to set it to false

To completely disable all session saving behavior, including the recording of session information, set browser.sessionstore.enabled to false:

• Type about:config in the Location Bar
• Press Enter
• Find browser.sessionstore.enabled
• Double click to set it to false

Privacy issues

Session Restore will restore connections to services which use session cookies to maintain login state, such as GMail. If someone else uses your computer after you, that person could access your personal information on those sites. If this is a concern, you should not enable the "Show my windows and tabs from last time" option described above.

You may also wish to disable the Session Restore crash recovery feature by changing the value of browser.sessionstore.resume_from_crash from true (default) to to false (explained above). This will prevent another user from restoring a previous session when Firefox is opened after a crash or other unexpected close, such as system shutdown while Firefox is running.

External links

• Session Restore (Firefox Support)
• Session Restore - MozillaWiki)
• Firefox3.1/AboutSessionrestore Security Review - MozillaWiki
• Session store API - MDC
• Discussion of the SessionSaver extension for Firefox

Related bug reports

• Bug 333907 - XRE quits too abruptly when Windows is shut down
• Bug 448976 - turn the Session Restore prompt into an error page
• Bug 501995 - Not prompted for session restore after force-quitting due to lock-up