Rollover
Rollover is the number and pattern of simultaneous keys a keyboard can report correctly. The practical limit may vary across different areas of the key matrix.
Keyboard rollover tester.
See every signal.
Press several keys together and see exactly which physical inputs reach this browser. Find blocked combinations, record your peak, and test the shortcuts that matter.
Start testingBuild a combination.
Watch what arrives.
The tester focuses automatically. Hold keys together, then release the full combination to add its largest simultaneous set to your recent history.
No signal pulse? The page received no new keydown event. The operating system may have intercepted it, or the keyboard may have blocked that combination.
Rollover monitor
Keep this panel focused while holding key combinations
Signal 0
Current keys0
Peak observed0
Session statusBuild a combination
Held codesNone
EscF1F2F3F4F5F6F7F8F9F10F11F12
`1234567890-=Backspace
TabQWERTYUIOP[]\
CapsASDFGHJKL;'Enter
ShiftZXCVBNM,./Shift
CtrlWinAltSpaceAltWinMenuCtrl
PrtScScrLkPauseInsHomePgUpDelEndPgDn↑←↓→
Num/*-789+456123Enter0.
Idle Pressed
Recent combinations
- Release a combination to save it here.
Rollover, ghosting,
and blocking.
These terms describe different outcomes. Knowing which one you are seeing helps you test the right combinations and avoid misleading conclusions.
Ghosting
Ghosting is an unwanted key report: the system receives a key you did not press. Modern keyboards usually prevent this through matrix design and firmware.
Blocking
Blocking happens when firmware suppresses a conflicting key to avoid a false report. The missing key can look broken even though it works by itself.
Test the combinations
you actually use.
A large palm press is useful for finding a peak, but real shortcuts and movement patterns reveal whether the keyboard suits your work.
Start with a known chord
Hold two modifiers and add letter keys one at a time. Watch the signal, current count, and matching virtual keys.
Try gaming movement
Test W + A or D + Shift + Space, then add number-row abilities and any push-to-talk key used at the same time.
Test work shortcuts
Check the editing, design, audio, and development shortcuts that combine modifiers with letters, arrows, or function keys.
Repeat suspicious sets
Change one key at a time. A pattern that fails repeatedly is more informative than one missed event during a busy system moment.
What 6KRO and
NKRO really mean.
Marketing labels summarize capability, but the connection mode, firmware mode, operating system, and exact key pattern can affect what reaches an application.
6KRO
Six-key rollover guarantees at least six regular keys at once, usually alongside common modifiers. The familiar six-key limit comes from the USB HID boot-keyboard report format used for broad compatibility, not from an absolute limit of USB itself.
NKRO
N-key rollover means every key in the supported matrix can be reported independently. Modern keyboards can use richer HID reports or multiple report groups, but a browser test observes only the events delivered by the operating system.
Firmware modes
Some keyboards offer compatibility and NKRO modes. A BIOS-friendly mode may expose fewer simultaneous regular keys, while a performance mode uses a different report descriptor.
Connection modes
Wired, receiver, and Bluetooth modes may use different firmware paths or report formats. Compare each mode using the same combinations.
Where rollover
shows up.
The best test is a realistic one.
- Games. Movement, sprint, jump, crouch, abilities, and voice chat may overlap during one action.
- Rhythm play. Dense patterns can require many letter or number keys to register within the same moment.
- Creative software. Modifier-heavy commands often combine Shift, Control, Alt, arrows, and tool shortcuts.
- Accessibility. Alternative input techniques may depend on chords that ordinary typing never exercises.
- Shared keyboards. Local multiplayer can place several hands on one matrix, exposing combinations a single user would not reach.
Every received
code stays local.
The current set and recent combinations exist only in this tab. Nothing is uploaded or attached to an account.
0combinations transmittedOne result is
not a certificate.
A high observed peak is encouraging, but reserved shortcuts and untested matrix patterns mean a browser cannot certify complete hardware NKRO.
10recent combinations retainedFAQ
Answers about simultaneous keyboard input and browser limitations.
How do I test keyboard rollover?
Focus the tester, hold several keys, and verify that every matching position remains highlighted. Release the whole chord to save its largest simultaneous set.
Does seven detected keys prove NKRO?
No. It proves that one seven-key combination reached this browser. True NKRO describes broad matrix behavior, so test many patterns and treat the result as observational.
Why does a third key sometimes disappear?
The combination may collide in the keyboard matrix and be blocked by firmware, or a system shortcut may intercept it. Test the key alone and then change one key in the chord.
Can this test detect ghost keys?
If the browser reports a represented key you did not press, it would appear highlighted. However, this page cannot determine whether an unexpected event came from hardware, firmware, a macro, or software.
Why do Windows or screenshot shortcuts not appear?
The operating system can reserve combinations before websites receive them. No signal pulse means only that this page received no keydown event.
Do modifier keys count toward rollover?
This tester counts every distinct code it receives. Product 6KRO claims often describe six regular keys in addition to modifiers, so compare the on-page count with the manufacturer's exact definition.
Can connection mode change rollover?
Yes. A keyboard may expose different reports over wired USB, a wireless receiver, or Bluetooth. Test each mode with the same chords.
Are my combinations stored?
No. Current and recent combinations remain in page memory and disappear when you reset or leave the page.
Method and
further reading.
The tool maps browser-delivered physical key codes; it does not inspect the keyboard's USB report descriptor.
Browser key codes
MDN documents how KeyboardEvent.code identifies physical key positions independently of the printed character.
Test procedure
Read the NKRO, 6KRO, and ghosting guide to build repeatable combinations and interpret missing or unexpected events.
Try the chord
that matters.
Return to the tester, hold the full combination, and watch every signal that reaches the browser.
Test another combination