Added this since our company policy is to disable "Restore previous session" at startup with no possibility to change it, then, this application would have done the job with an option to automatically save at exit and load at startup, without it, If we forgot to save session before close it is better to use manual "Restore previous session" in Firefox menu, anyway, the extension does what it says then 4 stars, 5 if/when auto save and load is implemented.