In case you use "Clear history when Firefox closes" or otherwise clear history.

• do not clear the "Browsing history"

• Settings -> Privacy & Security
  Firefox will: "Use custom settings for history":
  [X] "Clear history when Firefox closes" -> Settings
• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

• using "Clear history when Firefox closes" in Firefox 102+ honors exceptions and keeps cookies with an allow exception, previous versions removed all cookies
• clearing "Site settings" clears exceptions for cookies, images, pop-up windows, and software installation and exceptions for passwords and other website specific data

On Mac closing Firefox can be more complicated because you can close all open windows, but keep Firefox running with the menu bar visible or minimized in the Doc.

Make sure to use "Quit Firefox" with all windows still open, especially if you want to use "Restore Previous Session". Otherwise check "History -> Restore Previous Session" and "History -> Recently Closed Tabs/Windows".

• https://support.mozilla.org/en-US/kb/restore-previous-session

Thank you but this does NOT apply to me nor does it look like my issue above was even read. I NEVER use "clear history". I have been using Firefox as a browser for 10yrs, I know what to do already but can't because of the above ISSUE. and RESTORE PREVIOUS SESSION or RESTORE PREVIOUS WINDOW typically work. As above, they are in the drop down menu but are DARK they are not active. WHY?? Recently closed TABS also is faulty - restores wrong tabs - Today, am asking why Session and Window are NOT active.

You aren't using Private Browsing mode?

Make sure Firefox isn't set to run in permanent Private Browsing mode (Always use Private Browsing mode; Never Remember History).

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

• Settings -> Privacy & Security
  Firefox will: "Use custom settings for history"
• remove checkmark: [ ] "Always use Private Browsing mode"

SETTINGS = "SAVE HISTORY". That's what is says. WHY?? Why can I NOT restore WINDOW or SESSION?

Maybe check the controlling sessionstore prefs in about:config to make sure that they are not zero.

• browser.sessionstore.max_tabs_undo
• browser.sessionstore.max_windows_undo

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Do the files in the sessionstore-backups folder in the Firefox profile folder get updated?

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

Yep. double checked. already using custom setting for "History" - box for Private Browsing was/is UN-checked.

Checked to "Open previous Windows at Start up" just to see IF the "Recently Closed Windows / Restore" might become active. going to re-start Firefox now.

Thanks for trying cor-el. appreciate the suggestions.

Do files in the sessionstore-backups folder in the Firefox profile folder get updated?

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

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.

• make sure to backup the current sessionstore.jsonlz4

You can look at this tool to inspect a compressed jsonlz4 sessionstore file. This tool works locally, no uploading is done.

• https://www.jeffersonscher.com/res/scrounger.html