You can check the settings in "Clear history when Firefox closes":

• Do not clear the "Browsing History".

• Tools > Options > Privacy: History: [X] Clear history when Firefox closes > Settings
• https://support.mozilla.org/kb/Clear+Recent+History

It is also possible that there is a problem with the files sessionstore.js and sessionstore.bak in the Firefox Profile Folder.

Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox Profile Folder.

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost, so you will have to create them again (make a note or bookmark them).

• http://kb.mozillazine.org/Multiple_profile_files_created

I already had it set to not clear my browsing history....

Did you check for problems with the sessionstore.js file?

• http://kb.mozillazine.org/sessionstore.js

App (pinned) tabs and Tab Groups (Panorama) are stored as part of the session data in the sessionstore.js file in the Firefox profile folder.

If you use cleanup software like CCleaner then check the settings for the Firefox application (e.g. Session).

I honestly don't know how to check that.

Hi janielouangela

the sessionstore.js file it is in Profile folder - Windows, find it and delete it.

(see the screenshot how the file looks like)

read for more in cor-el's relpy link

thank you

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder

It would make much more sense for mozilla/firefox to make it so even if you clear the history (for privacy sake and such) that your apps don't disappear. Isn't there a way to save certain sites that you have pinned so they don't get deleted when clearing history?

App tabs only disappear if you use "Clear history when Firefox closes" to make Firefox do this when you close Firefox.
Any other way to clear private data like history doesn't affect the App tabs.

• App Tab Initializer: https://addons.mozilla.org/firefox/addon/app-tab-initializer/
• Easy App Tabs: https://addons.mozilla.org/firefox/addon/easy-app-tabs/

Forget the profile - it's a setting in the general tab of the Firefox options dialog. You (and I) want it set to: "Show my windows and tabs from last time", not "Show my home page' or "show a blank page". It seems unlikely that Mozilla would override your settings in an upgrade (never did that in the past), so I suspect that you (perhaps unwittingly) installed an extension that hijacked your browser.

I know that the IMVU client will do that - they want to know everything about you (waiting for you to open their search page voluntarily doesn't produce the same amount of user data as hijacking your home page AND making that the default restart state).

Some extensions in this vein will reassert themselves after you've made changes to your browser settings. If that's the case, you'll have to find the offending extenion and disable or uninstall it.