If you’ve just updated to Google Chrome 78, when you hover the mouse over a tab you’ll now notice a card displaying tab title and domain name, previously Chrome used to show a tooltip only on hover over, these are called “tab hover cards” introduced by Google in Chrome version 78, you can disable them if you don’t like, here is how.

First things first, the feature is not fully complete and Chrome future versions will bring tab previews with name Tab Hover Card Images, similar to that exist in Microsoft Edge. And sometimes, Chrome doesn’t fully display the title on the tab if it is too long, Google is working to address that in development versions.
Disable Tab hover cards in Chrome 78 or later
1. Visit Chrome://flags page
2. Search for Tab hover, in the highlighted search results, for Tab Hover cards

3. Select “Disabled ” and restart the Chrome browser.
Do note the flags are temporary, may work for a couple of versions, after that they’ll disappear, this is a temporary solution only, we suggest you to get used to the hover cards feature.