GEARCHECK LABCompare two displays with the same steady pattern in separate browser windows, one on each screen.
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The page sends the same code values to each window. Matching RGB values do not guarantee equal physical brightness or colour because panels, profiles, HDR modes and viewing conditions differ. Grey steps help compare tonal separation, while a grid can reveal different apparent scaling. Synchronization shares only pattern choices through a same-origin browser channel; it is optional and does not discover or control your monitors. A popup blocker can prevent a new window; opening this URL manually also works.
This is a visual comparison, not colour calibration, a measured colour difference or a physical screen-size measurement. The browser cannot reliably enumerate and arrange every monitor without additional capabilities. Use system display settings for screen arrangement. No fullscreen flashing, automatic brightness changes or profile installation occurs. Stop synchronization or close the comparison windows when finished.
Device previews, recordings, selected files and report notes stay in your browser. Downloaded files remain on your device. Network tests send generated probes to GearCheck Lab. DNS lookup sends your requested public domain name and type to our server and the Cloudflare public resolver only after you start a query. Local recordings, drawings, files, device names and battery logs are not uploaded. Ordinary page requests and usage measurement are described in our privacy policy.