Screen Test
Hunt dead and stuck pixels on fullscreen colour, check backlight bleed on solid black, look for banding in a smooth ramp, measure what refresh rate you are actually getting, and watch a moving bar for ghosting. Nothing is uploaded.
What a web page can and cannot measure
so you know what these numbers are worth- Your panel model and brightness are invisible. Nothing here is read from the display. Everything is either drawn for your eyes to judge, or timed from frame delivery.
- Refresh rate is measured, not reported. Browsers do not expose it, so test 02 times real frames. That makes it a floor: throttling, a background tab or a busy machine all push it down.
- Response time needs a camera. Test 04 shows motion your eyes can judge, but a real grey-to-grey figure cannot be produced by software on the same machine.
- Use fullscreen and a dark room for the pixel and bleed tests. Browser chrome and reflections hide exactly the faults you are looking for.
Dead and stuck pixels
Go fullscreen, then click or press the arrow keys to move through nine solid colours. Look for a dot that stays the wrong colour on every one of them. A dead pixel stays black on white; a stuck pixel stays lit on black. Press Escape to come back.
Not fullscreen? Clicking a swatch still fills this page's viewport, which is enough to spot most faults. Fullscreen is only better because it removes the browser chrome.