Keyboard Test

How this keyboard test works

The on-screen keyboard below mirrors a standard full-size layout. As soon as you press a physical key, the matching key on screen turns solid to show it is currently held down. Release it, and the key settles into a lighter highlight that means it has been tested and successfully registered a press. Keys you have not touched yet stay in their default color, so a quick glance tells you exactly which parts of your keyboard you still need to check.

The counters above the keyboard track your progress: how many of the keys have been tested at least once, how many are being held down right now, and the largest number of keys you managed to hold at the same time. That last number matters more than it might seem, see the rollover section below.

Why a key might not light up

If you press a key and nothing happens on screen, there are a few likely explanations, roughly from most to least common.

• Debris under the keycap: crumbs, dust or hair can physically prevent the switch from making contact. This is by far the most common cause on mechanical and membrane keyboards alike.
• A worn or sticky switch: on rubber-dome keyboards, a switch that has seen heavy use can lose its snap and stop registering light presses.
• Liquid residue: even a small spill, once dried, can leave a sticky film that stops a key from returning fully or from making contact at all.
• A driver or OS-level remap: some keyboards or utilities let you disable or reassign individual keys. If a key used to work and suddenly stopped, check your keyboard software before assuming it is broken.
• Ghosting or key rollover limits: if a key only fails to register while several other keys are held down at the same time, see the rollover explanation below. It is very likely not a broken key at all.

Ghosting and key rollover, explained

Most keyboards are wired as a grid of rows and columns rather than one wire per key, which keeps manufacturing cheap but has a side effect: press the right combination of three or more keys at once and the keyboard controller can lose track of which ones are actually down. This is called ghosting, and the maximum number of keys a keyboard can reliably report at the same time is its rollover (often written as NKRO for full n-key rollover, or 6KRO for a common six-key limit on USB keyboards).

Use the "max held at once" counter on this page to get a rough feel for your keyboard's rollover: hold down an increasing number of keys in different areas of the board (not all in one row or column, which trips ghosting sooner) and watch how high the counter climbs before an extra key stops registering. Gamers and fast typists usually want a keyboard with high rollover on the keys they use most; for everyday typing, occasional ghosting on obscure key combinations is rarely noticeable.

Want to measure this precisely? Use the dedicated key rollover and ghosting test, which tracks the maximum number of keys you can hold at once.

A note on the Fn key

You may notice the Fn key is not part of the on-screen layout. That is not an oversight: on the overwhelming majority of laptops, Fn is a hardware-level key that never generates a standard keyboard event at all, browsers included. It is handled entirely inside the keyboard controller before your operating system, let alone a web page, ever sees it. If you need to confirm your Fn key works, the reliable way is to test an Fn shortcut with a visible effect, for example a brightness or volume key, and watch for that effect rather than a key highlighting anywhere on screen.

Fixing a stuck or unresponsive key

Before assuming a keyboard needs replacing, these steps solve the majority of stuck-key problems.

For the full step-by-step process, including keycap removal and liquid-spill recovery, see the complete guide to fixing a stuck or unresponsive key.

• Turn the keyboard upside down and gently tap the back, or shake it lightly, to dislodge loose debris.
• Use a can of compressed air at an angle around the affected key, not straight down, to blow crumbs and dust out from the sides.
• For a keycap that lifts off (most mechanical keyboards and many laptops), remove it carefully with a keycap puller or a flat tool wrapped in cloth, clean underneath with a cotton swab and a small amount of isopropyl alcohol, let it dry fully, then reseat the keycap.
• If liquid was spilled, power the device off immediately, disconnect the battery if possible, and let it dry completely (24 to 48 hours) before testing again. A key that still feels sticky after drying usually needs a proper cleaning or a technician's help.
• Re-run this test after each step. If a key still will not light up after cleaning, and other keys around it work fine, the switch itself has likely failed and the key (or the whole keyboard, on many laptops) needs replacing.

Common keyboard problems at a glance

ANSI vs. ISO layouts

This tool uses the ANSI layout (the standard US keyboard shape), which has a rectangular Enter key and a single-row left Shift. Most of Europe uses the ISO layout instead, with a taller, L-shaped Enter key, a shorter left Shift, and an extra key next to it. If your physical keyboard is ISO and a key near Enter or the left Shift does not seem to match up visually, that is expected: the underlying key codes this tool reads (via the browser's KeyboardEvent.code) still identify each physical key correctly regardless of layout, only the on-screen shape differs slightly.

Testing a second-hand or work keyboard before you rely on it

If you are buying a used mechanical keyboard, inheriting one from a colleague, or just want to make sure a keyboard that has been sitting in a drawer still works before an important call, a full sweep with this tool takes under two minutes and catches almost everything that matters.

• Start with the function row and number row: these get less daily use than the letter keys, so a fault here often means the keyboard was damaged rather than simply worn out.
• Work through every letter, holding each one briefly rather than tapping, so a switch with a weak or delayed contact still has time to register.
• Press each modifier on both sides separately: left and right Shift, Ctrl and Alt are wired independently, and it is common for only one side to fail.
• Check the arrow keys and the navigation cluster (Insert, Home, Page Up, Delete, End, Page Down): these sit at the edge of the board and take more accidental knocks and spills than people expect.
• Toggle Num Lock and test the numeric keypad in both states, since a keypad key that seems dead is often just sending a different code than the one you expected, as explained in the FAQ below.
• Finish with a rollover check: hold down four or five keys spread across different rows and columns at once and confirm the "max held at once" counter climbs, rather than freezing at two or three.

Mechanical, membrane and scissor-switch keyboards

The keys light up the same way on this tool no matter what is physically underneath them, but the failure patterns differ enough to be worth knowing before you start troubleshooting.

Membrane keyboards (the rubber-dome type found in most budget and laptop-adjacent external keyboards) tend to fail gradually: a key that used to need a light tap starts requiring a firm press, and eventually stops registering altogether as the dome loses its shape. Scissor-switch keyboards, used in most modern laptops, are membrane keyboards with a stabilizing scissor mechanism under the keycap; their most common failure is debris or a small amount of liquid getting under one specific key rather than a general wearing-out. Mechanical keyboards, which use an individual physical switch per key, usually fail one key at a time rather than gradually across the whole board, and are also the easiest to repair yourself, since keycaps and often the switches themselves can be pulled and replaced individually.

Privacy and browser support

This test uses the standard Web KeyboardEvent API, supported in every current desktop browser (Chrome, Firefox, Safari, Edge and their derivatives). No keystrokes, key combinations, or any other data leave your device: the whole test runs in JavaScript in your own browser tab, and nothing is logged, stored, or transmitted. On mobile devices without a physical keyboard attached, the on-screen layout still displays for reference, but there is no on-screen touch keyboard to test since the tool is built to test a physical device.

For the full details on what is and is not collected, see our privacy policy.