Keyboard Tester
Test every key, rollover and key chatter online. Runs in your browser.
About this keyboard tester
This keyboard tester shows every key light up on an on-screen keyboard as you press it, so you can find dead keys, stuck keys and keys that double-type. It is for anyone checking a new mechanical keyboard, a second-hand laptop, or a board that suddenly started typing "tthe".
It goes further than a picture of a keyboard. You get the exact event.key and event.code values for developers, a rollover test that counts how many keys register at once, and a chatter warning when one press arrives twice.
Everything runs in your browser. Keystrokes are shown on screen and never stored or sent anywhere.
Features
ANSI and ISO layouts, full size or compact
Switch between the US-style ANSI layout and the ISO layout with the L-shaped Enter and the extra key next to left Shift. Hide the number pad for tenkeyless and laptop keyboards.
Left and right keys told apart
Each key is matched by its physical code, so left Shift, right Shift, left Ctrl, right Ctrl, both Alts and the number pad Enter all light up on their own.
Key codes for developers
The last key panel shows event.key, event.code, location and whether the press is an auto-repeat. The event log keeps the last 40 keydown and keyup events with the time since the previous press of the same key.
Rollover and ghosting test
Hold keys down one after another and the tester counts how many are registered at the same moment. It remembers your best run and shows which keys were in it.
Key chatter warning
If a key sends two presses faster than your threshold (50 ms by default, adjustable from 20 to 150 ms), it turns red and the warning lists it.
Shortcuts blocked only in the test area
Inside the test box, keys like Tab, Space, F5 and Backspace are captured so they don't scroll or reload the page. Click outside, or press Esc then Tab, and your keyboard works normally again.
How to use the keyboard tester
- 1Pick ANSI or ISO and the keyboard size, then click the on-screen keyboard.
- 2Press every key once; tested keys turn yellow, and the log shows key and code.
- 3Hold several keys together to test rollover, and watch for red chatter warnings.
When to use it
Checking a new or used keyboard
Press every key once until the counter reads 104 of 104 on a full ANSI board, or 87 on a tenkeyless one. Any key that stays white is dead or not reaching the computer.
Diagnosing double typing
Type normally for a minute. A red key with a chatter count is a switch that bounces. Cleaning or replacing that switch usually fixes it.
Testing a gaming keyboard's rollover
Hold W, A, Shift and Space together, then add more. If the count stops rising while you add keys, you have found the keyboard's limit.
Developer reference
Look up the event.code a key sends, or see how event.key changes with Shift, AltGr or a non-US layout.
How do I test my keyboard online?
Pick the layout that matches your keyboard, then click the on-screen keyboard so the test area has focus. Press each key once. Tested keys turn yellow, a held key turns blue, and a key with chatter turns red.
Work row by row and check the counter. Don't forget the second Shift, Ctrl and Alt, the number pad Enter, and the keys around the arrows. If a key never lights up, try it in another app too: if it is dead there as well, the problem is the keyboard, not the browser.
What is key rollover and ghosting?
Rollover is how many keys a keyboard can report at the same time. A keyboard using the standard USB boot report can send six normal keys plus the modifier keys (Ctrl, Shift, Alt and the Windows or Cmd keys) at once, which is called 6-key rollover. N-key rollover (NKRO) means every key can register together.
Ghosting is the opposite problem: on cheap keyboards, some three-key combinations make a fourth, unpressed key appear, or block a key you did press. Many keyboards prevent ghosts by simply ignoring the blocked key, so in this tester a blocked combination shows up as a key that refuses to light while others are held.
What is key chatter and how do I fix it?
Chatter is when one press of a key registers as two or more. The metal contacts inside a switch bounce for a few milliseconds, and keyboards normally filter that out. A worn, dirty or damaged switch can bounce for longer, and the extra press gets through.
Nobody presses the same key twice within 30 ms on purpose, so very short gaps point at the switch. Try these fixes in order:
- Blow out dust under the keycap, or remove the cap and press the switch 50 times quickly to clear it.
- Update the keyboard's firmware or raise its debounce time in the maker's software, if it has a setting.
- On hot-swap mechanical boards, replace the switch. On soldered boards and laptops, a repair shop can.
event.key vs event.code: what's the difference?
event.code is the physical key position, named after the US layout, so the key right of Tab is always KeyQ, even on a French AZERTY keyboard. event.key is the character that key produces with the current layout and modifiers, such as "a" on AZERTY or "Q" with Shift.
Use code for game controls and shortcuts tied to position, and key for text. The location value tells left (1) and right (2) modifiers apart, and 3 means the number pad.
Why use Mavros
| Mavros | Typical upload sites | |
|---|---|---|
| Layouts | ANSI and ISO, full size or no numpad | One US layout |
| Left and right modifiers | Shown separately by physical code | Often merged |
| Key codes | event.key, event.code, location, repeat | Key name only |
| Rollover test | Live count, best run and the keys in it | Rare |
| Chatter detection | Adjustable threshold with a per-key count | None |
| Page shortcuts | Blocked only inside the test area | Tab and F5 can leave the page |
| Keystrokes stored | Never, nothing leaves the browser | Not stated |
Tips
- Some keys never reach a web page. Fn is handled inside the keyboard, and the system may grab Print Screen, the Windows key and media keys before the browser sees them.
- On a Mac, other keys don't send a release while Cmd is held, so the tester clears held keys when you let go of Cmd.
- Once every key works, see how fast you type with the typing speed test.
- A noisy mouse switch shows the same double-click problem. The mouse test checks for it, and the dead pixel test rounds out a full laptop check.
Questions
How do I know if a key on my keyboard is broken?
Press it in the tester. If it never lights up while the others do, the key is not sending anything. Try it in a text editor too; if it fails there as well, the switch, the keycap contact or the keyboard's wiring is at fault.
Why does the Fn key not light up?
Fn is processed inside the keyboard and never sent to the computer. No website or app can detect it. Test it by pressing Fn with a function key and checking that the media or brightness action happens.
How many keys can a normal keyboard press at once?
A keyboard using the standard USB boot report sends up to six normal keys plus the modifiers at once. Many office keyboards are lower in some key groups because of their wiring. Gaming keyboards often support N-key rollover.
What threshold should I use for chatter?
Start with 50 ms. Real double-taps of the same key are rarely faster than about 80 ms, while switch bounce usually shows gaps under 30 ms. Raise it if you only want to catch obvious faults, lower it for fast typists.
Does the keyboard tester work with laptop keyboards?
Yes. Pick No numpad if your laptop has none. Laptop keyboards often have lower rollover than desktop boards, so a limit of 3 or 4 keys in some combinations is normal for them.
What is the difference between ANSI and ISO keyboards?
ISO keyboards have a tall, L-shaped Enter key and one extra key between left Shift and Z, for 105 keys in full size. ANSI keyboards have a wide single-row Enter, a long left Shift and 104 keys. ISO is common in the UK and Europe, ANSI in the US.
Does this site record what I type?
No. Key events are shown on the page and kept only in the tab's memory for the log. Nothing is stored or sent, and closing the tab clears it.