It's hard to know what is going on with your Firefox. If you can't find the sessionstore-backups folder, you may be looking in the wrong place. Are you opening your profile folder from the Troubleshooting Information page? Either:

• "3-bar" menu button > "?" Help > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, find the Profile Folder row and click the "Open Folder" button to launch your profile folder in File Explorer.

Here you definitely should find a sessionstore-backups folder. It should contain a very recently updated recovery.jsonlz4 file. Any luck tracking that down? You can back it up on your desktop "just in case."

It's late here, so I'll mention as an emergency measure, you can bookmark all the tabs in each window. Press Ctrl+Shift+D and give a name to the folder to bookmark all the current pages. This doesn't save the Back button history, but it's better than nothing.

Thanks for helping me troubleshoot this problem.

I confirmed that I am looking in the correct profile folder. When I do a recursive search for "session" I get sessionCheckpoints.json and session-state.json.

A recursive search for "recov" or "prev" returns nothing.

I have fiddled with config values in the past but currently when I open about:config and filter by "session" all values are the defaults.

Are there config values that would cause this problem?

You can use code in the Browser Console to get current session data (including PB mode tabs) and save this data to a text file.

• "3-bar" menu button or Tools -> Web Developer
• https://developer.mozilla.org/en-US/docs/Tools/Browser_Console

ssj = SessionStore.getBrowserState(); // get Current Session State
ssj = prompt("Copy Current Session State\n\nPaste New Session State: press ESC or click Cancel to abort", ssj||"");
if(ssj){SessionStore.setBrowserState(ssj)}

Uncaught ReferenceError: SessionStore is not defined

   <anonymous> debugger eval code:1

You might be using the Web Console, which is the one that opens in the lower part of the current tab. The Browser Console is a separate window which -- once you enable the command line -- allows access to browser internals like your session. More details in the article cor-el linked.

The sessionrestore-backups folder is deleted when Clear All History is run. Is this a bug?

The sessionrestore-backups folder is deleted when Clear All History is run. Is this a bug?

I think if you want to clear Browsing History for the time range Everything, it is appropriate for Firefox wipe the session history files. However, the bug is that if you set the dialog to clear as little as 1 Hour, Firefox also clears all of the files. This is a known problem but not a high priority to fix.

As long as you are still in session, Firefox should start saving new session history files shortly thereafter.

The session files should be deleted, but the problem is that the sessionstore-backups folder is deleted and not re-created. I see recurring failures to write to the folder in the browser console. The failures continue until I manually create the folder.

Hmm, I don't know why that is happening. When I test in an alternate profile, the folder isn't deleted. I guess file a bug report? https://bugzilla.mozilla.org/

You aren't using any external cleanup or other software that might be removing this folder ?