Keyboard Tester / Keyboard ghosting test
Keyboard ghosting test
Click the box and hold down as many keys as you can, then keep adding more. The number shown is the most keys your keyboard, cable and computer reported at the same moment. If it stops at 6 you have 6-key rollover, and if it reaches 10 or more the board is effectively unlimited. Ghosting is a keypress that fails or a key that appears out of nowhere when many are down.
0keys held now
0most at once
none
What it means
Hold several keys at once to measure.
Keys at your maximum
none yet
Key chatter
None flagged.
Event log
Ghosting, rollover and N-key rollover
Ghosting happens when you press several keys and the keyboard reports the wrong set: a key is missing, or an extra key appears. Rollover is the number of keys that are read correctly together. N-key rollover (NKRO) means any number of keys, limited only by your fingers. 6-key rollover (6KRO) is common on USB keyboards because the standard boot report holds six regular keys plus modifiers.
Why it happens
Cheap keyboards scan a grid of rows and columns instead of wiring every key on its own. When three keys of a rectangle are down, the grid can see a fourth, and without a diode at each key the controller cannot tell them apart. Better keyboards add diodes (anti-ghosting) or scan differently. Separately, the USB protocol many keyboards use in "basic" mode limits how many keys can be sent at once, and wireless links add their own limits.
How to run the check
- Click the box so it is listening.
- Hold the keys you really use at once, for example W, A, Shift, Space and a few more for a game.
- Add keys with your other hand until the "held now" number stops rising. Modifier keys count too.
- Lift everything, then try another spread of keys across the board; some keyboards limit certain groups.
Keys held at your maximum are listed so you can see which combination stopped. An operating system or driver can also cap the count, and the browser only passes on what it receives.
Reading the result
Under 6 usually means a basic keyboard or a limited wireless link. 6 to 9 is typical of a USB keyboard in standard mode. 10 or more suggests full NKRO, which gaming and typing-heavy boards often offer through a switch or a USB mode. A keyboard may offer NKRO only over cable. You can check individual dead keys on the keyboard tester.
Questions people ask
How do I test keyboard ghosting?
Hold several keys together in the checker above and watch the held and maximum counts. Ghosting shows as keys that fail to register when more are down, so a maximum lower than the number of keys you are pressing is the sign.
What is N-key rollover?
It means the keyboard can report any number of keys pressed at once without dropping or inventing keys. In practice, a result of 10 or more in this test is the usual way to confirm it.
Is 6-key rollover enough for gaming?
For most games, yes. Few games need more than 4 or 5 keys plus modifiers at the same time. Fast typists may notice dropped letters on boards with weak rollover.
Why does my keyboard only register 4 keys at once?
Cheap boards without diodes can lose keys that share rows and columns, and some wireless connections or power-saving modes limit the report. Try a cable, another USB port and a different key spread.
Does the result depend on my computer?
Partly. The keyboard decides most of it, but the connection (cable or wireless), the USB mode and the system driver can lower it. Test on a second computer to separate the keyboard from the setup.