Firefox always lost tab session. For example when browser crashed. Or site try to open new window in background, etc.. Why firefox just can't save session in sessionstore-backups that I can restore session for one day before for example After crashing I have previous.js recovery.bak recovery.js with the same content NO chance to recover multiple tabs an groups of tabs. I tried to replace sessionstore.js - nothing. I tried to: History -> Restore Previous Session - it's grayed out. As I understand user should create a backup script which will copy this files each time with current date and no one chance do this natively (included in browser by default)