Why Some Keys Are Not Detected in Browsers

Some keys never produce a keyboard event in a browser. The keyboard may be working perfectly while the operating system or browser handles the input first.

System and browser reserved shortcuts

Combinations such as Alt+Tab, Ctrl+W, and many Fn layer shortcuts are consumed by the operating system or browser. The web page never receives the event, so no online test can display it.

Fn keys and media keys

The Fn key on many laptops is handled by firmware or the OS driver and is not exposed to browsers. Media keys such as volume and brightness often produce events only on certain operating systems and browsers.

What to do instead

Retest a missing key in a text editor, on a second keyboard, and with a different browser. If it works outside the browser, the key is detected at the system level even though the test page cannot see it. The keyboard key test explains event.key and event.code for the events that do arrive.