In Opera, when you hover the mouse cursor over a tab, it shows the thumbnail of the web page in that tab. The thumbnail generation can slow down an older and slower computer. You can disable the showing of thumbnails of tabs by following these steps :
- Run your Opera browser.
- Click the red colored Opera menu button on the top-left.
- From the popup menu, select Settings → Preferences as shown
This would open the Preferences window. You can also press Ctrl + F12 to open the Preferences window.
- In the Preferences window, select Advanced → Tabs tab.
- Uncheck the checkbox labeled Show thumbnails when hovering tabs as shown,
- Click on OK to save the settings.