This keyboard tester shows an on-screen keyboard that lights up as you press keys. Each key you test stays marked, so you can work through the whole keyboard and see at a glance which keys have not responded.
It also reads out the details your browser receives for each press: the key code, the key value, the keyboard side and the legacy key number. You can hold many keys at once to see how many your keyboard can register, and the tool counts key repeats and detects chatter, where a single press registers twice.
Use it when you buy or build a keyboard, after spilling something on a laptop, or when a key seems to miss presses. Nothing you type is sent anywhere: the page only reads key events locally and shows them on screen.
Reviewed by: CalcMojo Editorial Team
How to use the keyboard tester
- Choose a layout: Full size (104-key ANSI with numpad) or Laptop / compact (no numpad). Pick the one that matches your keyboard.
- Press Start capturing keys. While capturing is on, the page blocks browser shortcuts for the keys you press, so keys like Tab, F5 or the arrows do not move the page.
- Press every key. A key is orange while held down and turns green once it has been tested.
- The counter above the keyboard shows how many keys you have tested out of the total in the layout.
- Press Stop capturing keys to get your normal shortcuts back, or Reset all to clear the results and test again.
What the readout means
For each press the tool shows four values taken from the browser's keyboard event.
- code identifies the physical key, regardless of the layout or language. The key right of Tab on a US keyboard is always
KeyQ, even on a French keyboard where it types A. - key is the character or action the key produced with the current layout and modifiers, such as
a,A,EnterorShift. - keyCode is the older numeric code. It is deprecated, but many programs and guides still quote it, so it is shown for reference.
- location tells you which copy of a key was pressed: Standard, Left, Right or Numpad. This is how the tester tells the left Shift from the right Shift, or the number row 1 from the numpad 1.
Ghosting and rollover
Keyboards detect presses with a grid of switches, and cheaper designs cannot tell some combinations of keys apart. Ghosting is when a key you did not press appears to be pressed, or a key you did press is ignored, because of how several keys overlap on that grid. Rollover is the number of keys a keyboard can register at once: 2-key rollover is very limited, 6-key rollover (6KRO) is common, and N-key rollover (NKRO) registers every key.
To test it, press and hold as many keys as you can at the same time, using both hands. The Most held at once figure shows the highest number of keys the tester received together. If you were holding seven keys and it reports four, your keyboard (or the connection, the operating system or the browser) dropped three.
Two cautions. The result is the whole chain, not only the keyboard: some operating systems and wireless links limit simultaneous keys even when the hardware could do more. And a normal typing keyboard rarely needs more than a handful of keys at once, so a modest figure is not a fault. It matters mostly for gaming, where several keys are held together.
Chatter and key repeat
Chatter (also called double-typing or switch bounce) is when one press produces two. It usually points to a worn or dirty switch. The tester counts a press as chatter when the same key goes down again within a short time of being released. The default window is 50 milliseconds, and you can change it. Humans rarely press the same key twice that fast on purpose, so a few chatter events on one key is a useful warning. Because fast typists can double-tap quickly, raise or lower the window to suit what you are testing.
Auto-repeat is normal: hold a key and the operating system keeps sending presses after a short delay. The counter simply totals those events so you can see them. Repeat speed and delay are set in the operating system, not by the keyboard.
Keys the browser cannot see
Not every key will light up, and that does not always mean it is broken.
- The Fn key and many laptop function shortcuts (brightness, volume, keyboard backlight) are handled inside the keyboard and are never sent to the browser.
- Some keys are caught by the operating system first. The Windows key, Alt+Tab, Ctrl+Alt+Delete and screenshot shortcuts may not reach the page. On Windows, PrintScreen often reports only a key-up event; the tester still marks it as tested.
- Media keys, power and sleep keys usually do not report to web pages.
- Phones and tablets have no physical keys, so connect a hardware keyboard to test it.
If a key does not respond here, test it somewhere else, such as a plain text box or another program, before you decide it is faulty.
Layouts and what counts as a key
The full layout has 104 keys: the standard US ANSI 101 keys plus the two Windows keys and the Menu key. The laptop layout leaves out the numpad and the navigation block, and keeps the arrow keys and a Delete key, since laptops fold the rest behind the Fn key. If your keyboard has extra keys such as a second row of macros or an ISO layout with a taller Enter key, those will register in the readout but may not be drawn on the diagram.
Keyboard care tips when a key misbehaves
Turn the keyboard upside down and gently shake out crumbs. Use compressed air between the keys. For a sticky key on a laptop, isopropyl alcohol on a cotton swab around the edge of the keycap works for many cases, but check the maker's guidance first, because laptop keys differ. If one specific key keeps chattering, the switch is probably worn, and on a mechanical keyboard the switch can often be replaced.
Frequently asked questions
How do I test if all keys on my keyboard work?
Press Start capturing keys and press every key. Each one turns green when the browser receives it. Keys that stay unlit either did not register or are keys the browser cannot see, such as Fn.
Why does the Fn key not light up?
The Fn key is processed by the keyboard's own firmware and does not send a normal key event to the browser, so no web page can detect it. The same applies to many laptop brightness and volume shortcuts.
What is keyboard ghosting?
Ghosting happens when pressing several keys at once makes the keyboard report a wrong key or miss one, because of how the key switches are wired. Hold many keys together and compare the number you hold with the number the tester reports.
What does 6KRO or NKRO mean?
6KRO means the keyboard can report up to six keys pressed at the same time. NKRO means N-key rollover, so every key can be reported at once. Basic keyboards may only manage two to four.
What is key chatter?
Chatter is a single press registering as two or more, usually because a switch is worn or dirty. The tester flags a key when it is pressed again within the chatter window (50 ms by default) after release.
Why does the page stop my shortcuts while I test?
While capturing is on, the tester cancels the browser's default action for each key so that keys like Tab, F5 or Space do not scroll or reload the page. Press Stop capturing keys to get them back.
Is anything I type recorded?
No. The page reads key events in your browser and displays them on screen. Nothing is stored or sent to any server.
Does it work for non-US keyboard layouts?
The key code identifies the physical position, so it works for other layouts, and the key value shows the character your layout produced. The diagram is drawn in US ANSI positions.
Sources & Methodology
- MDN: KeyboardEvent.code — physical key identifiers used for the on-screen layout
- MDN: KeyboardEvent.key — the character or action value shown in the readout
- MDN: KeyboardEvent.location — standard, left, right and numpad locations
- MDN: KeyboardEvent.repeat — how auto-repeat events are told apart from new presses
- Chatter rule: a new, non-repeat key-down of the same key less than the chatter window after its key-up. The 50 ms default is CalcMojo's own starting point, not a standard, and is editable. Rollover guidance is general background, not a measured specification for any keyboard.
Data accurate as of: November 2026