Try to rename the sessionstore-backups folder in the profile folder.

cor-el said

Try to rename the sessionstore-backups folder in the profile folder.

Thank you. That resulted in a clean start. Unfortunately, once I had opened and closed some tabs, the closed tabs were still there when I restarted Firefox.

Thank you all who replied. For those using a Linux system, the solution is to remove ' %u' from the command to launch Firefox.

Note that if you remove the '%u' then you won't be able to open external links in Firefox or drag file to the Firefox launcher.

cor-el said

Note that if you remove the '%u' then you won't be able to open external links in Firefox or drag file to the Firefox launcher.

Thanks. I don't know what that means. So far, no issues which could be one of those. I may have to choose between the lesser of two evils.

I have discovered that the file sessionstore.jsonlz4 was NOT re-created after I renamed it. The folder sessionstore-backups was recreated.

This problem has recurred even with the amended command, i.e. removing the string '%u'.

ender21 said

This problem has recurred even with the amended command, i.e. removing the string '%u'.

Does your Firefox complete its standard shutdown file maintenance? This includes:

(1) A new file named sessionstore.jsonlz4 appears in the profile folder (main level)

(2) The recovery.jsonlz4 and recovery.backlz4 files are removed from the sessionstore-backups folder

jscher2000 said

ender21 said

This problem has recurred even with the amended command, i.e. removing the string '%u'.

Does your Firefox complete its standard shutdown file maintenance? This includes:

(1) A new file named sessionstore.jsonlz4 appears in the profile folder (main level)

(2) The recovery.jsonlz4 and recovery.backlz4 files are removed from the sessionstore-backups folder

Thank you. 1. A new file named sessionstore.jsonlz4 is present. 2. The recovery.jsonlz4 and recovery.backlz4 files are still present in the sessionstore-backups folder. There is also a file previous.jsonlz4 which is earlier in time than the other files, one of which is a minute earlier in time. It may help if I attach a screenshot.

Hi ender21, I don't know why you have the older recovery.jsonlz4 and recovery.backlz4 files if you just shut down Firefox recently. They either should have the current date, or they should have been removed after sessionstore.jsonlz4 was created. Strange.

jscher2000 said

Hi ender21, I don't know why you have the older recovery.jsonlz4 and recovery.backlz4 files if you just shut down Firefox recently. They either should have the current date, or they should have been removed after sessionstore.jsonlz4 was created. Strange.

Thanks and sorry. I last used Firefox Quantum at about the times shown. I subsequently reverted to Firefox 56 on another system, using a different profile folder. Before that, at one point after exiting the browser there was no file named sessionstore.jsonlz4.

Did you compare the file date/time of the sessionstore.jsonlz4 file and the recovery files in the sessionstore-backups folder?

Did you recently try a new profile?

cor-el said

Did you compare the file date/time of the sessionstore.jsonlz4 file and the recovery files in the sessionstore-backups folder? Did you recently try a new profile?

Thanks. The sessionstore.jsonlz4 file is the same date as the other files (July 22, 2018) and time is 8:39AM that day. The recovery.baklz4 time is 8:38AM and the recovery.jsonlz4 time is 8:39AM. I did create a new profile for Firefox Quantum and last used it on April 18, 2018.

I have been using a method suggested by a user on mozillazine who had the same problem.

I grab the unwanted tab and drag it off the tab bar whereupon it opens in a new window. I then close that window.

Unfortunately, all that achieves is that it stops that particular tab from appearing in a subsequent session. Other unwanted tabs still appear in most sessions.

This issue has been resolved. I commented out the importing of a .css file which made the tab bar multi-rowed. I did that because I was having trouble moving tabs to where I wanted them.  The unexpected side effect was that tabs previously closed no longer appeared in the next session.