How to use the n-key rollover test
- Click the test area. The n-key rollover test runs in your browser: it’s free, and there’s nothing to install.
- Free mode: hold as many keys as you can and watch the count. “Most at once” keeps the highest number of regular keys that registered together, and the map outlines them.
- Guided mode: press Run rollover check and follow 4 short steps. Hold the keys shown, then let go. Each step reports the keys that registered and any that dropped out.
- Read the verdict under the test: NKRO, 6KRO or limited, with what it means for games and typing.
- To check an NKRO setting, press Save as Run A, switch the setting on your keyboard, and run the test again. The verdict shows both runs side by side.
Press Esc twice to leave the test area. Press Copy result to save the numbers for a review or a return.
What is n-key rollover?
N-key rollover (NKRO) means a keyboard reports every key you hold, no matter how many. A keyboard with 6-key rollover (6KRO) reports up to six regular keys plus modifiers. “Rollover” is how many keys can be down together before new presses stop registering. Gaming keyboards add NKRO because players often hold several movement and action keys at once, and a dropped key can cost a move.
- 2KRO keyboards, mostly old or very cheap ones, register two keys reliably.
- 6KRO is the standard USB limit and covers most office and many gaming keyboards.
- NKRO keyboards register every key you hold, even with both palms on the keys.
How the key rollover test works
This key rollover test counts physical keys from the browser’s keydown and keyup events. When you hold a key and its keydown never arrives, the keyboard or the operating system dropped it.
Modifiers (Shift, Ctrl, Alt and Win or Cmd) are counted apart from regular keys. That’s how the keyboard rollover test shows “6 keys + 1 modifier” for a 6KRO keyboard instead of a confusing 7.
Ten fingers can only hold about ten keys, so the last guided step asks you to press both palms flat on the keyboard. The browser adds no limit of its own: the number you see is what your keyboard and operating system report. The layout you pick only changes the drawing; the count works with any layout.
6KRO vs NKRO: what’s the difference?
The limit comes from the standard USB keyboard report, which every computer understands, even a BIOS setup screen. The report is 8 bytes long:
- 1 byte for modifiers, with one bit for each of the 8 modifier keys
- 1 reserved byte
- 6 slots for regular keys
When you press a seventh regular key, a 6KRO keyboard fills every slot with an error code (called “rollover”). The computer ignores that report and keeps the last valid one, so the seventh key never appears. Modifiers still work because they have their own bits.
NKRO keyboards send a larger report that can list every key. Most games need fewer than 6 keys plus modifiers at once, so 6KRO is fine for them. Rhythm games, stenography and two players sharing one keyboard benefit from NKRO.
N-key rollover vs anti-ghosting
Ghosting is when a keyboard reports a key you didn’t press. Anti-ghosting stops those phantom keys with diodes on each switch, or by blocking combinations that could cause them. A blocking keyboard can still drop some combinations. NKRO keyboards neither ghost nor block, and the keyboard ghosting test shows which combinations your keyboard drops.
Understanding your results
| Verdict | What it means | What to do next |
|---|---|---|
| NKRO | 10 or more keys registered together. | Nothing: your keyboard reports every key. |
| 7+ keys | More than the USB 6-key limit. | Run the palm step to confirm full NKRO. |
| 6KRO | Six regular keys plus modifiers, and a seventh dropped. | Fine for most games. Look for an NKRO mode if you need more. |
| 6 keys | Six keys at once, not yet confirmed. | Run Guided mode: step 2 confirms the limit. |
| Limited | Keys dropped before six. | That’s matrix blocking: run the keyboard ghosting test. |
An exclamation mark on a key means it appeared without being asked for: a possible ghost key, or a key you brushed by accident. Repeat the step to be sure. If a step fails, press Retry and hold the keys again. A finger that slipped looks the same as a dropped key.
How to turn on n-key rollover
Start with your keyboard’s manual or support page. Many gaming keyboards switch between 6KRO and NKRO with an Fn shortcut or a setting in their software. Many confirm the switch with a short light blink. Test before and after: if more than six regular keys register, NKRO is on.
Keyboards with QMK firmware enable NKRO with NKRO_ENABLE = yes in the build options, and the NK_TOGG keycode switches it on and off.
Rollover can differ between a USB cable and a Bluetooth or 2.4 GHz wireless connection, so test each connection you use.
Some BIOS and UEFI setup screens, KVM switches and older systems only understand the 6-key report. Many NKRO keyboards switch to that report by themselves when a BIOS asks for it. If yours stops working there, switch it back to 6KRO for that job.
Rollover on Windows, Mac and laptops
Windows keeps the Windows key and Alt+Tab for itself. In Chrome and Edge, press Capture system keys to include them. Pressing Shift 5 times opens the Sticky Keys prompt, and holding right Shift for 8 seconds opens the Filter Keys prompt. Choose No, then click the test area to continue.
Mac: macOS sends no key-up for keys pressed while Cmd is held, so the test releases them when Cmd comes up.
Laptops often block some 3-key combinations, because their keyboards rarely have a diode for each key. If a single key doesn’t register at all, check it with the keyboard tester first.