The Intrusive Preview
In Ubuntu, the default file manager (Nautilus, also known as Files) includes a built-in preview system designed to help you quickly identify media. When you open a folder containing video files (.mp4, .mkv, .webm), Nautilus doesn’t just show a static thumbnail. If you click once to select the file, or sometimes simply hover over it depending on your exact desktop environment configuration, Ubuntu might attempt to automatically open a miniature playback preview within the file manager itself, or launch the default video player (like Totem) if you accidentally double-click when you meant to drag. This is incredibly frustrating if you are trying to organize a massive folder of video clips, as the constant attempt to buffer and play the files slows your system to a crawl.
Disabling Media Generation and Previews
To speed up your file browsing and stop Ubuntu from automatically opening or previewing videos when you navigate directories, you must restrict Nautilus’s thumbnailing behavior.
Open the Files (Nautilus) application. Click the hamburger menu (three horizontal lines) in the top-right corner of the window and select Preferences. A new dialogue box will appear. Navigate to the Search & Preview tab (or just the “Preview” tab on older versions of Ubuntu). Look for the section labeled Thumbnails. You will see an option for “Show thumbnails.” By default, it is likely set to “All files.” Click the dropdown menu and change it to Never (if you want maximum performance) or Local files only (if your issue is with network drives). Below that, find the Sound Files section. Ensure the “Preview sound files” option is unchecked or set to Never. By disabling these automatic media checks, you can click, drag, and manage your video files as plain data without triggering any playback software.