Hi Mihael, I could offer a guess: Firefox has a feature called "tear-off tabs" which will detach a tab to a new separate window if you move it up or down from the tab bar by about half a tab height.

Do you think that is what happened?

There isn't any feature to disable tear-off tabs, but there is an add-on that can "undo" detached tabs by re-attaching them. So this might help if you run into this problem regularly:

https://addons.mozilla.org/firefox/addon/disable-tab-detach/

You can drag the tab back to the Tab bar in the original window to undo the 'tear off'. Firefox will automatically close the now empty window.

Thank you for taking your valuable time to share your advice/experience! Of course, I will get back with you if your solution solves it or not. Again, thank you for taking your valuable time to follow-up!

Is there a way to disable the memory-sparing feature that puts open tabs in "inactive"" mode when they are not the currently-viewed tab? My open tabs are going "inactive" way too quickly, and it's not due to a lack of memory resources on my computer--I have plenty of high-speed RAM and a good GPU.

Also, can you tell me why the Firefox-Tab-Suspender app is listed as a "not recommended" extension? I have not been using it so far:

"This is not a Recommended Extension. Make sure you trust it before installing."

I read the explanation of the reasons why an extension might be categorized this way, but don't know how it applies to this particular extension.

Thanks!

Hi scolburn, what version of Firefox are you running? Currently, the feature to suspend tabs due to low memory is disabled by default. You can check yours here:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

(2) In the search box above the list, type or paste unload and pause while the list is filtered

(3) If the browser.tabs.unloadOnLowMemory preference is bolded and has a value of true, double-click it to restore the default value of false

scolburn said

Also, can you tell me why the Firefox-Tab-Suspender app is listed as a "not recommended" extension? I have not been using it so far:

"This is not a Recommended Extension. Make sure you trust it before installing."

There is a small number of Recommended extensions. The others are not Recommended. That doesn't mean they are bad or good, just that they do not get the careful human review that Recommended extensions do, so Mozilla can't tell you whether they are safe (there are automated checks, and an initial human review, but updates sometimes introduce new behaviors).