Is My HDMI Working?
Detect connected displays, check resolution, pixel ratio, and screen arrangement — all using the Window Management API in your browser.
This test uses the Window Management API to enumerate all connected displays and report each screen's resolution, pixel ratio, position coordinates, and whether it is the primary or an external monitor.
The Window Management API can detect up to 16 simultaneous displays with sub-pixel position accuracy, available in Chrome 100+ and Edge 100+ on desktop platforms.
Window Management API not supported. Showing basic screen info.
What Do Your Results Mean?
| Result | Range | Meaning |
|---|---|---|
| Good | All connected monitors detected with correct resolutions | Your HDMI/DisplayPort connections are working properly. The API shows each display's resolution, position, and pixel ratio matching your system display settings. |
| Warning | Fewer monitors detected than physically connected | A display may not be recognized by the OS. Check cable connections, try a different port, and verify the display is powered on. Also ensure Window Management permission is granted. |
| Bad | Only one screen detected or API not supported | The Window Management API requires Chrome/Edge 100+. If using a supported browser, your external display may not be detected by the OS — check display settings and cable connections. |
Common Issues and How to Fix Them
Only one monitor shown despite multiple displays connected
Grant the Window Management permission when the browser prompts. Without this permission, the API can only see the current screen. Check chrome://settings/content/windowManagement.
Resolution shown doesn't match the monitor's native resolution
The API reports the resolution set in OS display settings, not the panel's native resolution. Adjust scaling and resolution in System Display Settings to match the panel spec.
Test shows 'API not supported' error
Window Management API requires Chrome 100+ or Edge 100+. Safari and Firefox do not support this API. Update your browser to the latest version.