Monitor Ghosting Test

This test moves a bar across the screen at a fixed, constant speed and lets your own eyes judge what trails behind it. The position is calculated from elapsed real time on every animation frame rather than by stepping a fixed distance per frame, so the sweep speed stays the same whether your display runs at 60Hz or 240Hz — only the smoothness of the motion changes, not the speed.

What you are actually looking for lives on the physical panel, not in any signal your browser produces. Every pixel is a tiny cell that has to physically switch to a new color, and that switch takes a small but nonzero amount of time called the response time. When it can't finish before the next position needs to show, the previous color lingers behind the moving edge, fading out over the next few frames. That lingering color is what you see as a trail, and no camera or screenshot will ever capture it, because the video signal itself changes instantly — only the physical pixels lag behind.

The two patterns exist because that lag is rarely symmetric. Many panels can switch quickly from dark to light but comparatively slowly from light back to dark, or the reverse, and the specific weak direction varies by panel technology. The bright pattern on a black background exposes trailing in one direction, and the darker pattern on a gray background exposes it in the other, which is why testing both tells you more than either alone.

Judge what you see at your normal viewing distance rather than leaning in — ghosting is meant to be noticed in ordinary use, not hunted for under magnification.