Hi eyesblue, do you mean that you do not see any additional windows or tabs when you use one of these menu commands: * "3-bar" menu button > Restore Previous Session * (menu bar) History > Restore Previous Session If those items are missing or grayed, check either: * "Library" toolbar button > History > Recently Closed Windows (and within each restored window, Recently Closed Tabs) * (menu bar) History > Recently Closed Windows (and within each restored window, Recently Closed Tabs) Do those allow you to bring back any missing windows/tabs? ---- If that doesn't help... Could you check whether Firefox is creating/updating session history files? You can open your current Firefox settings (AKA Firefox profile) folder using 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, click the "Show in Finder" button. If Finder shows a short list of one or more semi-random folder names (e.g., a1v2c3d4.default), open the selected folder. Next, double-click into the '''sessionstore-backups''' folder. The kinds of files you may find among your sessionstore files are: * recovery.jsonlz4: the windows and tabs in your currently live Firefox session (or, if Firefox crashed at the last shutdown and is still closed, your last session) * recovery.baklz4: a backup copy of recovery.jsonlz4 * previous.jsonlz4: the windows and tabs in your last Firefox session * upgrade.jsonlz4-''build_id'': the windows and tabs in the Firefox session that was live at the time of your last update * various .js files from Firefox 55 or earlier Could you take a look at what you have and the date/time of the various files to see whether you think any of them would have the missing tabs from your last session? To preview the contents of a file, you can drag and drop it onto this page, then click Scrounge URLs: https://www.jeffersonscher.com/res/scrounger.html That tool is on my site, so please let me know if it doesn't work for you.