@cratte Mine uses a lot less. It depends on what you store there.

If you have open video or media tabs, the browser will store more data in your RAM (open streams) and possibly also in your local storage (stored media files or sections). You can limit the amount of cookies and data that is stored if you set Opera to delete it when you exit at: 'opera://settings/cookies' If you're storing website data on a drive with large file allocation sizes, smaller files will be bloated. I.e. each 0 b file become from 4 kb (normal drive setting) up to 2 MB+ (bad setting for browser drives). You could try to clear browsing data and use the Advanced option under 'opera://settings/clearBrowserData' to do a more thorough data clear. Note that this will make websites forget you, so you might have to log in again. If Opera is unable to clear this data for some reason, you can manually clear it at: '%LocalAppData%\Opera Software\Opera Stable\Cache' (Windows).