Check your settings to see what it's set at and if you click on a tab and pull on it - it will pop out of the current browser and to get it back you have to grab and drag back to the original browser. Otherwise your mouse is having issues.

Firefox has a feature called "tear off" tabs: when you pull downwards on a tab, after a certain point, it moves to a new window.

If you never intentionally move tabs to a new window, then you could consider this add-on -- it automatically "re-attaches" tabs back to their original window after they are torn off:

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

WestEnd said

Check your settings to see what it's set at and if you click on a tab and pull on it - it will pop out of the current browser and to get it back you have to grab and drag back to the original browser. Otherwise your mouse is having issues.

My first thought was the mouse acting up so I tried a new one. Same results. I seems like a sensitivity thing. Just went from rarely happening to several times per day.

I'll pick up another mouse tomorrow just in case I have two bad ones.

Like posted above by jscher2000, you tear off a tab to a new window if you drag the tab slightly down, possibly if you click the tab to select the tab. This is more an operation issue like a shaky hand than a mouse issue, you need to make sure not to drag a tab vertically to prevent this from happening. The extension mentioned above can undo this action and move the tab back and close the window (an extension can't prevent the tear off, but can undo this).

jscher2000 said

Firefox has a feature called "tear off" tabs: when you pull downwards on a tab, after a certain point, it moves to a new window. If you never intentionally move tabs to a new window, then you could consider this add-on -- it automatically "re-attaches" tabs back to their original window after they are torn off: https://addons.mozilla.org/firefox/addon/disable-tab-detach/

Thanks for the info. I'll install the addon and test it.

cor-el said

Like posted above by jscher2000, you tear off a tab to a new window if you drag the tab slightly down, possibly if you click the tab to select the tab. This is more an operation issue like a shaky hand than a mouse issue, you need to make sure not to drag a tab vertically to prevent this from happening. The extension mentioned above can undo this action and move the tab back and close the window (an extension can't prevent the tear off, but can undo this).

It seems more like a sensitivity issue than a sudden onset of a shaky hand. Been using Logitech trackballs for years so the hand is pretty much anchored. My concern it that this went from a thing that rarely happened by accident to several times per day suddenly.

Note that this is the same feature as Move to New Window in the Tab bar context menu (Move Tab). I don't know if the sensitivity is affected by the Density setting in the customize window.

I guess a quick update is in order. I installed the add-on and it seems to work fine.

Out of curiosity I switched to Chrome for a couple days. During the two days I never accidentally tore a tab off.