The test above checks whether every key on your keyboard reaches the browser. Click inside the tester to focus it, then press keys one at a time. Each key lights up on the on-screen U.S. ANSI layout while you hold it and stays marked once you release it, while the log lists the most recent eight key presses and the counters track distinct keys seen and the most keys held at once.
Use it when one key has stopped typing, when a key repeats or sticks, when a laptop board acts up after a spill, or when you want to know how many keys your board reports at the same time. No permission prompt is involved, and the Reset the tester button clears the layout, the event list, and all three readouts.
How the keyboard test works
The tester listens for the two events a browser fires for every key. The W3C UI Events specification defines keydown as the event dispatched when a key is pressed down and keyup as the event dispatched when it is released. The tester highlights a key on keydown, drops the highlight on keyup, and leaves a seen mark on any key that completed the pair.
The log shows two values per event. MDN describes KeyboardEvent.key as the value of the pressed key with modifier state, locale, and layout taken into account; printable keys report their character while control keys report names such as Shift or Enter, and KeyboardEvent.code as the physical position of the key, independent of layout and modifier state. MDN notes that the key producing q on QWERTY reports KeyQ, and so do the a key on AZERTY and the apostrophe key on Dvorak, which is why one U.S. ANSI drawing serves every reader.
The W3C recommendation UI Events KeyboardEvent code Values states that code values are based only on the key's physical location and do not vary with the user's locale. No permission prompt appears, because key events need no grant the way a camera does, nothing you press is recorded or uploaded, and the tester only sees events arriving in the focused tab. While the tester area has focus it claims every key, including Tab, so the page itself stays still while you test; click outside the tester or press Escape twice in a row to hand your keyboard back to the browser. Browsers fire repeated keydown events while a key is held, at an environment-dependent rate flagged with a repeat attribute, and this tester filters those repeats so a held key registers once.
How to read your results
A key that lights up blue while held and turns green after release is healthy from the switch through the operating system into the browser. Work across the board row by row until no unmarked keys are left on the drawn layout. The reference layout does not draw the numeric keypad, PrintScreen, Scroll Lock, Pause, or media keys; presses on those keys still register and appear in the event list.
A drawn key that never lights up and never appears in the event list is the clearest failure, because no event reached the browser at all. That points at the key, the keyboard, its cable or wireless link, a driver, or a system setting rather than at the app you were typing in. First make sure it is not half of a combination the system reserved.
The rollover counter shows the most keys the page saw held at once. Hold three or four together and it should match your fingers. If it stalls no matter which keys you add, the keyboard is not reporting the rest of that combination, which is how dropped input shows up in games and fast typing.
Two smaller readings matter. A run of log entries from a single tap means that key is chattering, and a key value that disagrees with the legend on the cap, which happens when the active layout differs from the layout printed on the caps, means the hardware is fine and the layout is translating.
If the test fails
Start by ruling out the test itself. Click inside the tester so it holds focus, then press the key alone, without Ctrl, Alt, Command, or the Windows logo key, since those are the combinations the system intercepts. For a second opinion from built-in tools, see how to test a keyboard on Windows and Mac.
Then separate wrong characters from dead keys. If keys register in the log but produce the wrong letters or symbols, the board is fine and the active input source is a different layout, which how to change your keyboard layout in Windows walks through.
If keys produce no event at all, work down the physical layer. Microsoft's guidance for mouse and keyboard problems in Windows is to unplug the USB cable and wait for the driver to unload before reconnecting it, try another port, remove any hub and connect directly, inspect the cable for damage, recharge or replace batteries, and update drivers through Windows Update or Device Manager. What that leaves is covered in how to fix a keyboard not typing.
When only a cluster of neighboring keys fails, or those keys need a hard press, treat it as contamination. Microsoft's same guidance says to make sure no dirt is blocking keys or sensors, and how to clean a keyboard covers doing that safely. Then run the test again and compare the distinct-key count.
Before buying a replacement, prove where the fault lives. Microsoft recommends connecting the device to another computer and confirming it works there, so if the same keys fail on a second machine the keyboard itself is at fault.
Platform notes for Windows and macOS
On Windows, three accessibility settings change how presses reach apps and can make a healthy keyboard look broken. Microsoft documents Filter Keys as ignoring brief or repeated keystrokes, Sticky Keys as letting commands such as Ctrl and S be pressed one key at a time, and Toggle Keys as an audio cue for Caps Lock, Num Lock, and Scroll Lock. All three sit under Settings, Accessibility, Keyboard on Windows 11 and Settings, Ease of Access, Keyboard on Windows 10.
Windows also reserves shortcuts for itself. Microsoft's shortcut reference documents Ctrl with Alt and Delete as the security screen, Alt with Tab as the window switcher, and dozens of Windows logo key combinations, so a key that stays unlit only inside one of those is not evidence of a fault. Microsoft's On-Screen Keyboard, opened from keyboard settings or with the Windows logo key, Ctrl, and O, lets you keep typing while you diagnose.
On macOS, the built-in second opinion is Keyboard Viewer. Apple documents opening it from the Input menu by choosing Show Keyboard Viewer, and enabling that menu in System Settings, Keyboard, Text Input, Edit if it is hidden. It shows an on-screen keyboard you can click or drive from the physical keys, and it updates as you hold Option or Shift.
Apple's Keyboard settings guide covers how fast characters repeat when you hold a key and how long the system waits first, and the same pane is where you add input sources for other languages. macOS reserves system shortcuts of its own, listed in Apple's Mac keyboard shortcuts reference.
Common questions
Why does a key stay unlit even though the keyboard works?
Usually because the combination belongs to the operating system or the browser rather than to the page. Microsoft documents Ctrl with Alt and Delete, Alt with Tab, and the Windows logo key combinations as shortcuts Windows handles, and Apple documents system shortcuts for macOS, so those events can be consumed before the page sees them. Press the key on its own before treating it as dead.
Why do the key and code columns disagree?
They answer different questions. MDN describes key as the value the key produces with modifiers taken into account, and code as the physical position of the key. On an AZERTY board the a key reports KeyQ, because that code names the position where q sits on a U.S. keyboard, which is why the tester can draw one layout and still light the right key.
Does the test record what I type?
No. The tester reacts to key events inside the page while it has focus, and nothing you press is recorded or uploaded. The Reset the tester button clears the highlighted keys, the event list, and all three readouts, and keys pressed while another window has focus never reach the page.
Official references
- MDN reference for KeyboardEvent.key
- MDN reference for KeyboardEvent.code
- W3C UI Events specification
- W3C UI Events KeyboardEvent code Values
- Microsoft guide to mouse and keyboard problems in Windows
- Microsoft guide to Sticky Keys, Filter Keys, and Toggle Keys
- Microsoft reference for Windows keyboard shortcuts
- Apple guide to Keyboard Viewer on Mac
- Apple guide to Keyboard settings on Mac
- Apple reference for Mac keyboard shortcuts
