N-Key Rollover Test
Hold as many keys as you can at once and see the highest number your browser registers together — a browser-observed rollover check, not a hardware verdict.
Rollover test
Hold as many keys as you can at once, then release them all. The peak is captured automatically.
0
keys held right now
Press keys anywhere on this page to begin. Focus this panel to keep Tab and Space inside the test; press Escape to leave it.
- No keys held
Reading your result
Hold a group of keys and let go to record your first attempt. Try several different groups — spread across the board, clustered together, and with Shift, Ctrl or Alt included — because a single combination can be blocked for reasons that have nothing to do with the keyboard.
Keyboard map
Keys held right now are highlighted. Keys registered at any point this session keep a marker, and the keys in your best set are outlined.
The interactive keyboard map appears here once the page's scripts have loaded.
Held right now Registered this session In your best set (dashed outline)
Attempt log
No attempts recorded yet. The chart appears once you have held and released at least one group of keys.
| # | Time | Keys at once | Non-modifier | Modifier | Peak held | Key set |
|---|---|---|---|---|---|---|
| No attempts yet — hold a group of keys and release them. | ||||||
Advanced: raw key data for the best attempt
Each row is one key from your highest-scoring attempt, exactly as the
browser reported it. code is the physical key position and does not change with
your keyboard layout; key is the character or name the layout produced.
| Key name | code | key | Type |
|---|---|---|---|
| No attempt recorded yet. | |||
No key events excluded.
Measurement environment
Timer resolution: — High-resolution timing: — Browser: — Platform: —
These conditions affect your result. A browser that rounds its clock to 1 ms cannot resolve sub-millisecond differences, so the hold times shown in the attempt log are quantised in this browser. The rollover count itself does not depend on clock precision. How we measure.
What this test cannot tell you
This runs in a web browser, so it can only count key events after your operating system has already delivered them. It cannot inspect your keyboard's report descriptor, read its firmware, or confirm what the hardware sent over USB or Bluetooth. A count of six is a strong hint at the classic six-key report format, not proof of it, and a high count proves only that the whole chain — keyboard, link, USB stack, OS and browser — carried that many keys together on that attempt.
It also cannot tell you why a combination failed. Shortcuts consumed by the operating system or the browser, accessibility features such as Sticky Keys, KVM switches, USB hubs and some wireless receivers can all reduce the number that reaches this page. Never read a single low attempt as a fault in the keyboard.
How to run this test properly
Click the test panel first, or press Tab until it is focused. While it has focus the page suppresses defaults such as Tab moving focus away and Space scrolling the document, which keeps your attempt intact. Press Escape to leave the panel.
Then hold keys down one at a time, keeping every one of them pressed, and release the whole group together. The peak count is captured automatically when the last key comes up, so you never have to press a button mid-attempt. Repeat with several different groups: letters clustered in one area, letters spread across the board, and groups that include Shift, Ctrl or Alt. Your result is the highest count from any single attempt.
What the number actually means
Six ordinary keys plus modifiers is the classic ceiling. The USB HID boot protocol describes a fixed keyboard report with one byte of modifier flags and six slots for regular keys, and many keyboards keep reporting in a report format of that same shape even when the boot protocol itself is not in use. That is why six is such a common answer.
So if your browser registers more than six non-modifier keys at once, the keyboard must be sending a report format that carries more than six. If it stops at exactly six across several different key groups, that is a strong hint at a six-key format — but only a hint, because the browser sees what the operating system chose to deliver, not what the hardware sent. Our guide on what N-key rollover means goes through the report formats in more detail.
Why modifiers are counted separately
In that standard report, Shift, Ctrl, Alt and the Windows or Command key are carried as individual flags rather than occupying the six key slots. A keyboard limited to six regular keys can therefore often register six letters and several modifiers at the same time, which is why a total of eight or ten is common on hardware that is still fundamentally six-key. This page shows both numbers — the total and the non-modifier count — so you can see which limit you actually reached.
Why a combination can fail for reasons that are not the keyboard
- The operating system claims combinations before any application sees them: Alt+Tab, the Windows or Command key shortcuts, and Ctrl+Alt+Delete are gone before the browser is involved.
- The browser claims others. A web page cannot cancel Ctrl+W or Ctrl+T, so those combinations will always cut an attempt short.
- Accessibility features such as Sticky Keys, Filter Keys and Slow Keys change how held keys are reported.
- KVM switches, some USB hubs, BIOS-style boot mode and a few wireless receivers force the six-key report format even on a keyboard that can do better when connected directly.
A low count therefore often describes the combination you picked, not the keyboard. Try again with a different group before concluding anything.
Rollover is not the same thing as ghosting
Rollover is how many keys can be reported at the same time. Ghosting is a different fault: a key you never pressed appears, or a pressed key is blocked, because of how the key matrix is wired without isolating diodes. Both feel identical while typing or gaming — keystrokes go missing — so it is worth running the keyboard ghosting test alongside this one. The guide on ghosting versus key rollover explains where the two overlap.
What "NKRO" claims on a spec sheet mean
Products advertise 6KRO, NKRO, or "NKRO over USB". Several keyboards ship in six-key mode by default and expose a firmware toggle or key combination that switches to the full-rollover report. If you consistently get six here and expected more, it is worth checking whether your keyboard has such a toggle, and whether it is connected directly rather than through a hub or switch. Re-run this test after each change — that comparison is something a browser test can genuinely tell you, because the conditions on your own machine stay the same between runs.
Related keyboard tests
Frequently asked questions
How many keys should register at once?
There is no single correct number. Six ordinary keys plus modifiers is the most common result, because that is the shape of the standard USB HID keyboard report. Keyboards that send a different report format can register more. A result of two or three usually means the combination you chose was blocked somewhere along the way, so try several different key groups before drawing any conclusion.
Does this test prove my keyboard has N-key rollover?
No. It shows how many simultaneous keys your browser received, and the browser sits at the end of a chain that includes the keyboard, the cable or wireless link, the USB stack and the operating system. A high count is good evidence that the whole chain carried that many keys at once. A repeated result of exactly six is a strong hint at the classic six-key report format rather than proof of it.
Why do Shift, Ctrl and Alt seem not to count?
In the standard keyboard report the modifier keys are carried as separate flags rather than in the six key slots, so they often register in addition to six other keys. This page counts them in the total and also shows the split between modifier and non-modifier keys, so you can see which limit you actually reached.
Why did some key combinations do worse than others?
Some combinations never reach the browser at all. The operating system claims shortcuts such as Alt+Tab and the Windows or Command key combinations, the browser claims others such as Ctrl+W, and accessibility features like Sticky Keys change how held keys behave. A low count can therefore describe the combination you picked rather than the keyboard.
What is the difference between rollover and ghosting?
Rollover is how many keys can be reported at the same time. Ghosting is a different effect, where a key you never pressed appears or a pressed key is blocked, caused by how the key matrix is wired. Both feel like missing keystrokes while typing or gaming, so it is worth running the ghosting test as well as this one.
Does this page store my keystrokes?
No. Everything runs inside your browser. The attempt log lives in the page until you reload or clear it, saving a result stores it only in your own browser's local storage, and nothing is ever uploaded.