You can use Private Browsing mode as that doesn't store session data in the profile folder.

• https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history

You can use Private Browsing mode as that doesn't store session data in the profile folder.

• https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history

Thank you very much!

This will work, but I'm concerned that then I will have to live with any limitations and restrictions that come with Private Browsing mode. Perhaps that won't be a problem, but I'm not sure.

However, this solution now got me thinking about another possibility ...

Where exactly in the profile folder is the session data stored? Perhaps I could always use a script to launch Firefox, with this script deleting the session data before performing the actual launch.

Is this a possibility?

You can possibly make the sessionstore-backups folder read-only.

You will normally find these files in the sessionstore-backups folder:

• previous.jsonlz4 (cleanBackup: copy of sessionstore.jsonlz4 from previous session that was loaded successfully)
• recovery.jsonlz4 (latest version of sessionstore.jsonlz4 written during runtime)
• recovery.baklz4 (previous version of sessionstore.jsonlz4 written during runtime)
• upgrade.jsonlz4-<build_id> (backups created during a Firefox update)

You can copy a file with Firefox closed from the sessionstore-backups folder to the main profile folder and rename the file to sessionstore.jsonlz4 to replace the current file, sessionstore.jsonlz4 is only present when Firefox is closed.

You can possibly make the sessionstore-backups folder read-only. You will normally find these files in the sessionstore-backups folder:

• previous.jsonlz4 (cleanBackup: copy of sessionstore.jsonlz4 from previous session that was loaded successfully)
• recovery.jsonlz4 (latest version of sessionstore.jsonlz4 written during runtime)
• recovery.baklz4 (previous version of sessionstore.jsonlz4 written during runtime)
• upgrade.jsonlz4-<build_id> (backups created during a Firefox update)

You can copy a file with Firefox closed from the sessionstore-backups folder to the main profile folder and rename the file to sessionstore.jsonlz4 to replace the current file, sessionstore.jsonlz4 is only present when Firefox is closed.

Thank you again, very much! This is a very promising possibility, and I will work on it during my spare time over the next few days and then report back here with my findings.

I am very upset with the Mozilla people for forcing us to go to such lengths simply in order to be able to always launch a fresh invocation of Firefox upon startup, if we so choose.

Yes, of course I know that the vast majority of Firefox users don't mind being forced in this way, but at least Mozilla should provide an *option* (perhaps in "about:config") so that the small minority of us who don't want this startup behavior to be shoved down our throats can *optionally* disable it.

But no.

Thank you, Mozilla, for being so awful and condescendingly paternaiistic to the Firefox user base.

In my spare time, I started working on manipulating the sessionstore-backups folder per the explanation above. I got part-way through the suggested work, but then I realized that I can solve this problem much more easily, in a completely different way:

Instead of using Firefox, I can just use the Seamonkey browser.

Assuming that my home page URL is "https://example.com/homepage" and that I have a Seamonkey profile called "myseamonkeyprofile", I can simply launch Seamonkey with a script that searches for and kills any running Seamonkey instances, and then starts Seamonkey as follows:

/path/to/seamonkey --profile ${HOME}/.mozilla/seamonkey/myseamonkeyprofile -new-window -url https://example.com/homepage

No matter how many open, active tabs there are when I exit, and no matter how I exit (via "kill -9", or via logging out, or via shutting down my computer and rebooting, or whatever), the next time I use that same launch command to start Seamonkey, it always starts up a fresh instance with that home page, and with nothing restored from the previous session.

I tried a parallel procedure with Firefox, starting it like this:

/path/to/firefox -new-instance -P myfirefoxprofile -new-window https://example.com/homepage

I ran it in a similar script which first kills any existing Firefox instances and then runs that command. But if I have an active Firefox session and then reboot, when I start Firefox this way after the reboot, it still restores the session that was active before the reboot.

I also tried this procedure with the Chromium browser, but it also restores my previous session after trying a simular procedure.

I didn't try the Chrome browser yet.

Anyway, I've decided now to abandon Firefox and use Seamonkey (or perhaps Chrome, if it turns out that I can prevent it from restoring sessions).

For many, many years, I've been happy using Firefox, but don't think that there's anything that I do in Firefox that I can't also do in Seamonkey.

If Mozilla ever stops being so unreasonable and finally decides to give us a selectable option for totally preventing session restore in 100-percent of the scenarios, I might then come back to Firefox.