Screen tests

Hunt for dead pixels and check that your monitor really runs at its refresh rate, full screen in your browser.

Dead pixel test Fill your screen with six solid colours, one click at a time, and spot any pixel that does not light up the way it should. 6 colours
FPS test Measures how many frames per second your browser draws, how steady they are, and shows motion at three speeds. Starts on its own. Live

Check a new monitor before the return window closes: the dead pixel test fills the screen with plain colours so a black, white or coloured dot cannot hide.

The FPS test then measures the refresh rate your browser actually gets. If a 144 Hz or 240 Hz screen shows 60, the cable, the port or the Windows display settings are usually the cause.