Keyboard Tester, Test Your Keys Online
Free online keyboard tester. Press any key to see it light up, inspect key codes, find dead or stuck keys, and check key rollover directly in your browser.
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A keyboard tester is the fastest way to find out whether every key on your keyboard actually works. Keys fail more often than most people think: a splash of coffee, years of dust building up under the caps, a worn-out switch or a loose membrane connector can all leave you with a key that registers intermittently, registers twice, or does not register at all. Before you buy a second-hand keyboard or laptop, after a spill, or when a game suddenly stops responding to a key, running every key through a visual test takes two minutes and tells you exactly where the problem is.
Frequently asked questions
How do I use the keyboard tester?
Why does a key on my keyboard not register?
What is the difference between event.key and event.code?
What is keyCode and why is it deprecated?
What is key rollover and what is ghosting?
How do I test how many keys register at once?
How can I detect key chatter (a key that types twice)?
Does the tester work with laptop and wireless keyboards?
Are my keystrokes sent anywhere?
Does it work with non-QWERTY layouts like AZERTY or Dvorak?
About Keyboard Tester, Test Your Keys Online
Using this tool is as simple as it gets: click anywhere on the page and start pressing keys. Each physical key lights up on the on-screen keyboard the moment you press it and stays marked as tested afterwards, so you can methodically work across the board and instantly spot any key that never changes colour. A live panel shows the technical details of every keystroke: the event.key value (the character or action the key produces), the event.code value (the physical key position, independent of your layout), the legacy keyCode number that older software still uses, the key location (standard, left, right or numpad) and the current state of the Shift, Ctrl, Alt and Meta modifiers.
The tester also measures key rollover, which is how many keys your keyboard can register at the same time. Cheap office keyboards often handle only two to four simultaneous keys before ghosting or blocking kicks in, while gaming keyboards advertise 6-key or full N-key rollover. Hold down as many keys as you can and the counter shows how many were actually detected, along with the highest number reached in the session. This matters for fast typists and gamers: if you have ever pressed three movement keys and jumped at the same time only for one input to vanish, rollover limits were the reason.
Everything runs locally in your browser, no keystroke ever leaves your device, which matters when you are typing test sequences on a machine you care about. The tool works with wired, wireless and laptop keyboards, with any language layout (the physical code is layout-independent), and includes the function row, navigation cluster, arrow keys and an optional numpad section. A few keys are reserved by the operating system or browser and cannot be captured, such as the Fn key (which never reaches the operating system) and certain OS-level shortcuts, and the tester handles those gracefully rather than hijacking your browser.
From Typewriter Jams to N-Key Rollover
The layout you are testing is over 150 years old. Christopher Latham Sholes patented the type-writer in 1868 and, together with his collaborators, gradually rearranged its alphabetical keys to reduce jamming: frequently paired letters were separated so their type bars would not collide when struck in quick succession. Remington put the resulting QWERTY arrangement into mass production in 1873, and it stuck. A popular legend claims the top row was arranged so salesmen could peck out the word TYPEWRITER using a single row, a story that is probably embellished but refuses to die. Rival layouts such as August Dvorak's 1936 design promise less finger travel, yet a century and a half of muscle memory has proven almost impossible to displace.
The electrical trick that makes rollover a problem dates from the earliest electronic keyboards. To avoid wiring every key individually, keyboards arrange their switches in a matrix of rows and columns; the controller scans the grid hundreds of times per second to see which intersections are closed. Press three keys forming an L shape in the matrix and the current can sneak along a path that makes a fourth, untouched key look pressed, the phenomenon known as ghosting. Manufacturers countered by blocking (ignoring the ambiguous press) or, in better keyboards, by adding a diode behind every switch, which isolates each key electrically and enables true N-key rollover, where every key on the board can be held at once and still register.
Keyboard testing has a surprisingly rich hardware heritage too. IBM's Model M, introduced in 1985 with its buckling-spring switches, is still prized by typists and collectors, and thirty-year-old units routinely pass a full key test today, one reason enthusiasts call it the tank of keyboards. Modern mechanical switches are typically rated for 50 to 100 million presses per key, but ratings assume clean laboratory conditions; in the real world, dust, crumbs and drink spills end far more keyboards than worn springs do. That is precisely why a quick browser-based test remains one of the most useful diagnostics you can run on any machine, old or new.