What ghosting and rollover mean
Rollover is how many keys a keyboard can register at the same time. Ghosting is when a key you press does not register, or a key you did not press shows up, because of how the keys are wired. Cheap keyboards share wires between keys, so some combinations block each other. Gaming keyboards add anti-ghosting for the keys games use most.
| Type | Keys at once | Common on |
|---|---|---|
| 2-key rollover | 2 plus modifiers | Basic office keyboards |
| 6-key rollover (6KRO) | 6 plus modifiers | Many USB keyboards in standard mode |
| N-key rollover (NKRO) | Every key | Gaming and mechanical keyboards |
How to run the test
- Press and hold keys one by one, without letting go. Watch the count go up.
- When a key you add does not appear, you have found the limit for that combination.
- Try the gaming combinations listed in the tool. Each one shows Works once all its keys are held together.
- Laptop keyboards often fail on combinations of three or more letters close together. That is a design limit, not a fault.
Getting more keys to register
- Many gaming keyboards switch between 6KRO and NKRO with a key combo or in their software. NKRO mode sometimes needs a USB connection rather than Bluetooth.
- Plug the keyboard straight into the computer, not through a hub.
- Browsers and operating systems handle NKRO fine, but some KVM switches limit it to 6 keys.
To check every key one by one, use the keyboard tester.
Frequently asked questions
Short answers to the questions people ask most about this test.
What is keyboard ghosting?
Ghosting is when some key combinations do not register, or register extra keys, because the keyboard wiring cannot tell them apart.
How do I know if my keyboard has n-key rollover?
Hold down as many keys as you can. If every key you add appears in the test, your keyboard has NKRO.
Why does my keyboard stop at 6 keys?
Many keyboards use the standard USB boot mode, which reports up to 6 keys at once plus modifiers. Check if your keyboard has an NKRO mode.