What the browser sees
The count below reflects events delivered to the page. Hardware matrix behavior, firmware, and OS handling can all change that number.
Keyboard Rollover Test
Rollover describes how many keys a keyboard can report while held. This workspace counts the keys the browser currently sees and records the highest simultaneous count.
Mobile note: Rollover testing requires a physical keyboard.
esc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12
` 1 2 3 4 5 6 7 8 9 0 - = backspace
tab Q W E R T Y U I O P [ ] \
caps A S D F G H J K L ; ' enter
shift Z X C V B N M , . / shift
ctrl win alt space alt win menu ctrl
Detected state
Browser view Current held 0
Maximum held 0
Held keys None
Limitations: this panel reports keyboard events delivered by the operating system to
this browser tab. It cannot measure hardware matrix behavior, firmware promises, USB polling, or true
physical latency.
About this test
Try realistic chords
Gaming and shortcuts use real combinations. Hold movement keys with modifiers and compare the detected count with the keys you actually pressed.
No unsupported claims
A browser test cannot prove a keyboard is NKRO. It can only show how many simultaneous keydowns reached the page in this session.
Related tools
Related guides
What is 6-key rollover?
It usually means the keyboard is designed to report at least six simultaneous keys. A browser test can detect what the OS delivers, not the hardware design promise.
Why does my count stay lower than expected?
Some combinations are reserved by shortcuts, and some matrix designs drop or alter keys. Test with plain letter and number keys first.
What is NKRO and how is it different from 6-key rollover?
NKRO stands for N-Key Rollover, meaning the keyboard can register every key pressed simultaneously, regardless of how many are held. 6-key rollover limits detection to six simultaneous keys, which is usually enough for most typing and gaming.
Can I fix a keyboard that doesn't register multiple keys at once?
Often yes. First, test on another computer or in a different USB port. Check if the keyboard has a gaming mode or driver utility that enables N-Key Rollover. If the issue continues, the keyboard hardware or membrane may be limited.
Does USB versus PS/2 affect simultaneous key registration?
Yes. Older USB keyboards often default to 6-key rollover due to USB HID protocol limits, while PS/2 connections can support more key presses. Many modern USB keyboards support N-Key Rollover using special drivers or beyond-HID protocols.