The Accidental Expose
In Ubuntu (using the default GNOME desktop environment), the “Activities” overview is the central hub for launching applications and switching workspaces. By default, there are two main ways to trigger it: pressing the Super (Windows) key, or forcefully shoving your mouse cursor into the extreme top-left corner of the screen (the “Hot Corner”). While the Hot Corner is intended for quick navigation, it is incredibly prone to accidental activation. If you are quickly moving your mouse to click the back button in a web browser, or trying to close a maximized window, you might overshoot slightly. The screen will immediately shrink your current window and explode into the Activities overview, completely breaking your concentration.
Disabling the Hot Corner
To maintain your focus on your active window and stop Ubuntu from automatically activating the Activities overview when your mouse hits the corner, you must disable the Hot Corner functionality.
Open the main application menu and search for Settings. In the left-hand navigation sidebar, scroll down and click on Multitasking. Look at the very top of the right-hand panel for the “General” section. You will see a specific toggle switch explicitly named Hot Corner, accompanied by the description “Open the Activities overview when the cursor is moved to the top left corner.” Click this toggle switch to turn it Off. The setting is applied instantly. You can test it by aggressively swiping your mouse into the top-left corner; nothing will happen, allowing you to click your browser buttons in peace. (You can still access the overview by pressing the Super key).