This how-to will show the steps for enabling/disabling overscan within the Raspbian operating system. Overscan is a legacy method to handle variable image presentation on CRT (cathode ray tube) TV’s and monitors, which is no longer needed on modern LCD monitors and TVs.
If the Raspberry Pi display does not fit your monitor/TV correctly (too large or too small), first check your monitor/TV’s aspect ratio and size to be sure it is set correctly. For a TV, this is usually done from the remote control. Monitors are typically changed from menu buttons.
If Raspberry Pi still slightly under- or over- fills the screen after confirming the monitor/TV is set correctly, then change the overscan as follows:
1. If Pi is running the GUI desktop screen, launch LXTerminal from the desktop or start menu.
2. At the command prompt type: sudo raspi-config and press Enter.
3. Arrow to option 8. Advanced Options and press Enter.
4. Press Enter on next screen on A1 Overscan.
5. If under-filling, move to <Disable> and press Enter. For over-filling, select <Enable> and Enter.
6. Tab to <Finish> and press Enter.
7. Reboot <Yes> press Enter.
Once properly set, the Raspberry Pi should fill the screen to its borders without cutting off any edges.