Firefox shows the full page title in a tooltip when you hover the mouse pointer over the tab for a bit. That's the classic way to figure out what page is behind a small tab without clicking the tab. I don't know of a way to turn off tooltips.

@Thaliel I had large drop down previews suddenly start appearing today. Is that what you're calling "graphic tab previews"? They were each about ¼ of the entire height of the monitor! I uninstalled Firefox, reinstalled, and now I've got what I think is the small "tooltip" described by jscher2000 which, like you, I would also like to disable. In any case, if what I'm describing is what you had/have, how did you disable "graphic tab previews"?* Cheers, Ian

• asking in case it returns!

I've always had small tool-tips appear as below. I suspect these are coming from my OS (Debian Linux) though as they are the same style as those I get when hovering over panel items.

To get rid of the new ones go to about:config and change browser.tabs.hoverPreview.enabled to false

Note that there are two control prefs in about:config. There is a second pref to control whether to show a thumbnail or only the two line tooltip with the URL or only the title:

• browser.tabs.hoverPreview.enabled
• browser.tabs.hoverPreview.showThumbnails

I don't personally use Firefox. However, I'm constantly needing to get Firefox to revert back to old behaviors for someone that needs things to stay relatively the same. This new feature of having the tab show anything when you hover over it is very distressing to this person. Much the same as the OP to this thread. I found the setting to turn off the Tab Preview Image. She said now it shows the name of the tab and the URL. So I searched in about:config and turned off Tab Preview altogether. However, it's still showing the URL on hover. The first responder above said they think that's called tooltips but there's no setting for tooltips anywhere that I can find. It's not a Windows thing as this feature didn't exist before.

So... How do I get that turned off. Nothing should ever display upon hover over the tab for my friend or anyone else like her.

If browser.tabs.hoverPreview.enabled is set to false then you only see the default tooltip that shows the full tab title.

For clarity, the screenshots are:

(1) Default setting: page title + site host name + thumbnail (2) With thumbnail turned off on the Settings page: page title + site host name (3) With hover preview turned off in about:config: page title (classic system-styled tooltip)