How to test a keyboard on Windows

Short answer: press every key on your real keyboard and watch which ones answer. A free app like Keyboard Tester draws the full 104-key board, turns working keys green and counts how many keys your keyboard can hold at once — rollover — in about a minute, fully offline.

Windows does not test your keyboard

When a key stops working, Windows offers no diagnostics at all: no panel shows which keys register, no report says “this key never fires”. Device Manager knows the keyboard only as one device — it will happily call it “working properly” even while half the keys are dead. That is why bookmarks full of “online keyboard test” pages exist: they are the quickest way to see which key answers. A small offline app is the honest tool for the job.

Method 1: online keyboard testers in the browser

Search for “keyboard test” and you will find pages that draw an on-screen keyboard and light up pressed keys. Good for a quick check, but with real limits:

you need a browser tab open — plus internet, plus a page that does not drown you in ads halfway through;
the browser sits between you and the keyboard: system shortcuts like Win, Alt+Tab or Ctrl+W are intercepted by Windows or the browser before the page ever sees them, so those keys cannot be tested honestly.

Fine for one suspicious key; tiring for a whole-board check.

Method 2: Keyboard Tester — full 104-key board, offline

Download free — KeyboardTester-Setup.exe

Press every key one by one — the matching key on the on-screen 104-key board turns green and stays marked until reset, so you can walk through the whole board and see what failed at a glance.
Hold several keys at once — the panel counts “held right now” and “max held at once”: the honest rollover number for games, fast typing chords and ghosting problems.
Check the last key and its USB HID code — shown in the status panel; handy proof for a warranty conversation or a key remap project.

No driver, no admin rights, no internet — everything runs locally.

Before a warranty claim or after a spill

Run the full board once and record the result — a photo of the layout with the dead keys marked beats “it feels broken” at any service centre.
After a spill, wait a day, then test every key once — most spills take out one or two keys, not the whole row; the board shows exactly which.
Hold your game's key combination together — if strafing plus shooting plus crouch stops registering, that is classic ghosting; the rollover counter gives you the number to quote.

FAQ

Is there a built-in keyboard test in Windows?

No. Windows has no panel or command that shows which keys register. Device Manager reports the keyboard only as a whole device, so a single dead key stays invisible to it.

Why do some keys not light up in an online tester?

Browsers and Windows itself swallow system shortcuts — Win, Alt+Tab, Ctrl+W — before the page sees them. An app that listens to raw key events, like Keyboard Tester, shows those keys honestly.

What does rollover mean, and what number is normal?

Rollover is how many keys a keyboard can report at the same moment. Office membranes often stop at 3–6 keys; good mechanical boards handle the full row. Presses beyond the limit are silently dropped — that is ghosting.

More: how to type emoji on Windows and how to test mouse clicks on Windows.