Tool

Keyboard ghosting and rollover test

Hold keys down together, one after another, and this page counts how many your keyboard reports at once. Where the count stops climbing is the keyboard's limit for that group, and a key you are holding that never lights is a ghosted key. Test the groups you actually press together.

Test three groups

  1. Click the page once, so it receives the keyboard.
  2. For games: hold W, A, S and D, then add Shift, Space and Control one at a time.
  3. For typing: hold A, S, D and F, then add J, K, L and the semicolon.
  4. Your own group: the keys you press together most, held one after another.
  5. Let go between groups and read most keys held at once after each.

Read the result

  • Six, then nothing. The basic USB report: six keys at once plus the modifiers. Most office keyboards work this way, and it is enough for typing.
  • Fewer than six, depending on the keys. Ghosting. The keyboard's wiring cannot tell some combinations apart, so it drops one. Laptop keyboards often do this with three or four letters held together.
  • Every key you hold. N-key rollover. Many keyboards sold for gaming report every key.

Ghosting only matters for the combinations you use. If your game keys and your typing keys all register together, the keyboard is fast enough for you.

If a combination drops a key

Climb this ladder, smallest step first:

  1. Try it on a cable. Some wireless keyboards report fewer keys at once than they do wired.
  2. Check the keyboard's own app. Some gaming keyboards switch between 6-key and N-key rollover in a setting.
  3. Move the binding. In a game, put the action that drops onto a key outside the crowded group.

What this test can miss

The page counts what the browser reports. Command, Control, Option and Alt combinations can be taken by the system or the browser before the page sees them, so test the letter keys and Shift first. On a Mac, keys released while Command is held send the page no release, so the tester lets go of them when Command comes up.

Give a spare key a job

On a Mac, InputConfig, the free app I make, can give keys you never use a job: open an app, run a macro, type a phrase. It listens to the keyboard and does not block or remap the key itself. The keyboard tester checks every key one at a time.

Questions

How do I test my keyboard for ghosting?

Hold down a group of keys together, one after another, and watch keys held right now. If it stops climbing before you run out of fingers, or a key you are holding never lights, that combination ghosts.

What is the difference between 6-key and N-key rollover?

A keyboard on the basic USB report sends at most six keys plus the modifiers at once. An N-key rollover keyboard reports every key, however many are held.

Which keys should I test together?

The ones you press together in practice: W, A, S, D with Shift and Space for games, and the home row for fast typing. Ghosting depends on the combination, so test more than one group.

Related

Download InputConfig on the Mac App StoreFree. macOS 14 or later. No account, nothing leaves your Mac. Open source on GitHub.