Keyboard Tester (Key Test and Rollover Check)
Press keys and watch them light up on an on-screen keyboard. Find dead keys, test ghosting and n-key rollover, and read key, code and keyCode values.
How to use
- Click anywhere on the page once so the window has focus, then press every key on the keyboard in turn. Each one turns green when it registers.
- Press any key still grey again; if it still does not light up, either the key is faulty or the operating system is taking its signal.
- To test rollover, hold the combinations you use in games (W, A, Shift and Space, say) and check that all of them light up and what the most-held count reaches.
- Read the last key's key, code and keyCode in the panel below, and press Reset to start over.
About this tool
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This page checks that every key on a keyboard registers. While a key is held its place on the drawn keyboard lights up blue, and once it has been pressed it stays green, so after running through the whole board any key still grey is one that never reached the browser. Above the board are the number of keys tested, how many are held right now, and the most held at once.
The simultaneous-press test matters for gaming. Hold several keys together: if one of them does not light up, the keyboard is blocking that combination, which is usually called ghosting. Laptop and budget keyboards share wiring between keys and commonly block particular three-key combinations, and a keyboard using the USB boot protocol reports at most six ordinary keys at a time (6-key rollover). A keyboard with n-key rollover (NKRO) should light every key you can reach, although the operating system, a USB hub or a Bluetooth link can lower the count again.
The panel below shows the last key's key (the character produced), code (the physical position), the legacy numeric keyCode, its location (left, right or numeric keypad) and whether it was an auto-repeat. Developers use it to see exactly what a key event carries: code stays the same whatever the layout, which suits shortcuts, while keyCode is deprecated and kept only for old code.
Keys that never reach the browser cannot be tested. A laptop's Fn key is handled inside the keyboard and sends nothing; the Windows key, Print Screen and some media keys may be taken by the operating system first. Language keys such as the Korean Hangul and Hanja keys arrive as right Alt and right Ctrl or as separate codes like Lang1 and Lang2, depending on the driver, and any code not on the drawing is listed under other keys. Browser shortcuts such as Ctrl+W cannot be intercepted, so avoid them. A key that types twice per press (chatter) is easier to spot by typing in a text editor.
Frequently asked questions
What are ghosting and n-key rollover?
Ghosting is the common name for keys that do not register when several are held at once. Keys share rows and columns of wiring, so the keyboard cannot tell certain combinations apart and blocks them. N-key rollover (NKRO) registers any number of simultaneous keys, and 6-key rollover registers up to six ordinary keys. If every key you hold lights up blue here, that combination is fine.
My Fn key or a language key does not respond.
The Fn key is handled inside the keyboard and never sends a signal to the computer, so no web-based test can see it. Language keys such as Korean Hangul and Hanja arrive as right Alt or right Ctrl, or as codes like Lang1 and Lang2, depending on the driver: check those keys on the drawing and the list of other keys.
How do key, code and keyCode differ?
key is what the keystroke produces, so it changes with Shift and the keyboard layout; code is the physical position on the keyboard and is the same in every layout (the Q position is always KeyQ); keyCode is a numeric value from older browsers, deprecated today but still common in older code.
A key types twice when I press it once.
That is usually chatter: a worn switch contact sends several signals per press. Press the key slowly a few times in a text editor and see whether characters double. On a mechanical keyboard, clean or replace the switch, and if the maker's software has a debounce setting, raising it slightly can help.
Are my key presses stored or sent anywhere?
No. Key presses are used only to update this page and are not stored or sent to a server. Closing or reloading the page clears everything.
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