Keyboard Tester

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How to use it

  1. Choose ANSI (the US layout, with a wide Enter and a long left Shift) or ISO (UK and most of Europe, with a tall Enter and an extra key next to the left Shift).
  2. Press every key. A key glows while you hold it and stays green once it has registered; the counter shows how many of the 104 (ANSI) or 105 (ISO) keys you have covered. Keys that never turn green are the ones to look at.
  3. To check rollover, hold down several keys at once (for example a whole row of letters) and read “Most at once”. To check for chatter, press a suspect key once, cleanly: if the page flags it, the key sent two presses.

How it reads your keyboard

Each key is identified by its physical position (the code of a keyboard event, defined by the W3C), not by the character it types, so the test works whatever language your keyboard is set to: the key right of Tab is KeyQ on a QWERTY, AZERTY or QWERTZ keyboard. Held keys that the system repeats (holding a letter down) are ignored, so one physical press counts once.

Rollover and ghosting

Rollover is how many keys a keyboard can report at the same time. USB keyboards in the basic “boot” mode, which every computer and BIOS understands, send at most six ordinary keys plus the eight modifier keys (Ctrl, Shift, Alt and the Windows or Command keys) in each report; when more are down, the USB HID specification has the keyboard report an error code instead of the keys. Many gaming and mechanical keyboards switch to a larger report for “n-key rollover”. Cheaper keyboards can also fail on particular combinations because of how their key matrix is wired, which shows here as a key you are holding not lighting up. Wireless and Bluetooth keyboards have their own limits.

Chatter

A worn, dirty or damaged key switch can bounce and send two presses for one, which shows up as doubled letters when you type. The page flags a press of a key that comes sooner after that key was released than the threshold you set (50 ms by default). Fast deliberate double taps can come close to that, so the flag is a prompt to test again slowly, not a verdict: press the suspect key once at a time and see if it keeps appearing.

What we tested

On October 15, 2026, in Chromium: pressing every key of each layout by its code marked all of them and the counter reached 104 / 104 (ANSI) and 105 / 105 (ISO); holding ten letter keys read ten at once, and an extra repeated key-down did not change the count; a second press 10 ms after release was flagged as chatter and one 120 ms after release was not; Ctrl+W was left to the browser while Tab was captured; the page fits a 390 px screen. Driving the page’s event logic with exact times, a 137.5 ms press read 137.5 ms, a re-press 49.9 ms after release was flagged and one exactly 50 ms after was not.

Sources

Frequently Asked Questions

How do I test my keyboard online?+
Press every key on your keyboard. Each key lights up while held and stays marked once it registers, and the counter shows how many of the 104 (ANSI) or 105 (ISO) keys you have covered. Keys that never light up are not reaching the computer.
What is key rollover?+
How many keys a keyboard can report at the same time. In the basic USB boot mode a keyboard reports up to six ordinary keys plus the modifier keys; many mechanical and gaming keyboards report more. Hold several keys at once and read Most at once.
What is key chatter?+
A faulty switch sending two presses when you press once, which shows up as doubled letters. The tester flags a second press that comes sooner after release than the threshold you set (50 ms by default).
Why does a key not light up?+
It may not be sending anything, or the system may keep it for itself: Fn never reaches web pages, and keys such as Print Screen or the Windows key can be taken by the operating system first. Try the key in another app to compare.
Does it work with any keyboard language?+
Yes. Keys are matched by their physical position, so AZERTY, QWERTZ and other layouts all light up the right place on the US or ISO drawing.
Is anything I type sent anywhere?+
No. The tester runs in your browser and keeps nothing.

Built by Derek Giordano · Part of Ultimate Design Tools

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