That should be the default. Is it possible you changed the settings?

Restore previous session - Configure when Firefox shows your most recent tabs and windows

FredMcD said

That should be the default. Is it possible you changed the settings?

No I need a extra option to automatically restore last session on next start when browser crashed on last run...

FredMcD said

Restore previous session - Configure when Firefox shows your most recent tabs and windows

I checked this page before but it does not solve my problem...

Check out these links; https://www.bing.com/search?q=firefox+Restore+Session++crash firefox Restore Session crash - Bing

There is a pref that sets the number of times Firefox will automatically try to restore session after a crash.

You can set via this pref on the about:config page when to show the sessionrestore page after a crash has occurred or the Task Manager was used to close Firefox (a value zero means to always show the sessionstore page).

• browser.sessionstore.max_resumed_crashes

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config

cor-el said

There is a pref that sets the number of times Firefox will automatically try to restore session after a crash. You can set via this pref on the about:config page when to show the sessionrestore page after a crash has occurred or the Task Manager was used to close Firefox (a value zero means to always show the sessionstore page).

• browser.sessionstore.max_resumed_crashes

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config

So I should set what value to force the browser to automatically restore session and open tabs?