Monitor Test: Free Online Check for Pixels, Lines and Bleed

A monitor test fills your screen with solid colors, fades and a moving block, so faults stand out. Use our browser test first, then your monitor's built-in self-test, which runs with no computer connected. If a fault shows in the self-test, it's the monitor itself.

Check it now with the white screen test

Fixes to try (easiest first)

Run our full-screen test
Go through the solid colors, fades and moving block. Note anything that looks wrong. [1]
Run the monitor's built-in self-test
Unplug the video cables and run the self-test from your monitor's manual. If lines appear during the self-test, there's a hardware issue with the panel. [1]
Check your pixel policy
If you find faulty pixels, check your manufacturer's allowance. Dell, for example, allows 0 bright pixels on UltraSharp monitors, and pixel defects are only covered during the warranty period. [2]

Is it worth fixing?

If the self-test is clean, the monitor is fine and any problem is the computer, cable or settings. If the self-test shows a fault, contact the manufacturer while it's under warranty.

Repair or replace? Try the calculator · Not sure this is your problem? Take the quiz

Sources

Last checked: October 21, 2026