Check the events your keyboard sends.
Capture key presses in a controlled surface, identify stuck keys, and see how many simultaneous inputs reach the browser.
Keyboard event bench
Ready for a keyboard test
Click the capture area, type several individual keys, then hold a combination to check browser-visible rollover.
Operating-system shortcuts and some media/function keys can be intercepted before a web page receives them. Their absence here does not prove a hardware fault.
Distinguish a missed key from a reserved shortcut.
Web pages do not receive every operating-system key. Test ordinary letter and number keys before drawing conclusions from media or function keys.
Compare the same key in a text editor and inspect the active keyboard layout.
Release all modifiers, refocus the test, then reconnect the keyboard.
Try different key groups; matrix limits often affect only specific combinations.