The setting "Show tab previews in the Windows taskbar" shows a hover thumbnail preview for each tab instead of for each window.

Go to about:config in the address bar and make sure browser.taskbar.previews.enable is set to true and browser.taskbar.previews.max is default 20.

Regardless of whether I enable it or not, this is what I get

Can you post what you see in both enabled and disabled?

See the comments in the source code.

• https://searchfox.org/mozilla-release/source/browser/modules/WindowsPreviewPerTab.sys.mjs

Does it still happen in a new profile? An easy way to test a new profile is to install Developer Edition and see if it happens there or refresh your existing profile.

Does it still happen in a new profile? An easy way to test a new profile is to install Developer Edition and see if it happens there or refresh your existing profile.

I then tested my current profile with only ten tabs. Didn't make a difference.

Then I restarted in about:support > troubleshoot mode. Didn't make a difference.

You can check for problems with preferences. You can delete possible user.js and numbered prefs-##.js files and rename/remove the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in current Firefox releases.

You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page (Root directory).

• Help -> More Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

I believe I found the answer, an answer I'm confident you already know, unless, of course, the results also still reflect some of my preference choices.

It's all about the tab limit.

12 tabs or less (first image)

13-20 tabs (second image)

More than 20, a single mousehover thumbnail, as I originally posted

This maximum is et via browser.taskbar.previews.max as mentioned above, so maybe we should have asked how many tabs you have.

This maximum is et via browser.taskbar.previews.max as mentioned above, so maybe we should have asked how many tabs you have.

The way it is currently constructed, it only makes sense to work this way, insofar as the thumbnails are concerned. When you consider the 12 tab limit, what the mouse hover would produce beyond that number wouldn't be discernible due to the shrunken size needed to get them to display all at once.

If your going to have this feature, I'd like to see the mouse hover produce the tabs thumbnails that surround the active tab, like five on each side, no matter what location that tab occupies in the tab bar list. That make more sense to me. Otherwise it's really just not very useful. Very limited.

BTW, if the max number is increased, you don't get more thumbnails, but the list of tab "links" on the mousehover increases, if your interested in that sort of thing.

cor-el said

This maximum is et via browser.taskbar.previews.max as mentioned above, so maybe we should have asked how many tabs you have.

Yes, I was referring to zeroknight's (thanks zeroknight!) comment. I started thinking about it, and decided to test things out.

The way it is currently constructed, it only makes sense to work this way, insofar as the thumbnails are concerned. When you consider the 12 tab limit, what the mouse hover would produce beyond that number wouldn't be discernible due to the shrunken size needed to get them to display all at once.

If your going to have this feature, I'd like to see the mouse hover produce the tabs thumbnails that surround the active tab, like five on each side, no matter what location that tab occupies in the tab bar list. At least this way, it would work regardless of how many tabs you have. That make more sense to me. Otherwise it's really just not very useful. Very limited.

BTW, if the max number is increased, you don't get more thumbnails, but the list of tab "links" on the mousehover increases, if your interested in that sort of thing.