Keyboard rollover test

As soon as you hold down one or more keys on your physical keyboard, the four counters above update in real time without requiring you to click inside a text box:

• Keys currently down: Displays the exact count of physical switches held down at this millisecond, accompanied by live scan-code badges (such as KeyW, ShiftLeft, or ArrowUp) in the active panel below.
• Max simultaneous: Records the largest multi-key chord your hardware successfully delivered at one time during the current session, along with the full list of scan codes that formed that record chord.
• Unique keys tested & total key presses: Counts how many distinct switches you have exercised and how many discrete non-repeating actuations occurred since your last reset.

Because the listener inspects KeyboardEvent.code on the window object and filters out event.repeat, holding a single key down for ten seconds still counts as 1 key held and 1 press. If you switch applications or minimize the browser while holding keys, the blur listener releases the active badges automatically so stale keys never linger on screen.

Different workflows place very different demands on simultaneous key reporting. Use the table below to compare what your software expects against what your keyboard delivers:

1. Exercise 1 — The 8-finger home-row press: Rest all eight fingers on A S D F J K L ; and press them down together, then add both thumbs on Space and AltRight. If the counter stops at 6 while holding 8 letters, your keyboard is running in standard 6-key USB HID mode.
2. Exercise 2 — Diagonal sprint + jump check: Hold KeyW + KeyA (up-left diagonal) and tap Space, ShiftLeft, KeyQ, and KeyE. Repeat with KeyS + KeyD and ArrowUp + ArrowLeft + Space. Many office laptops allow W + D + Space but silently drop W + A + Space or ArrowUp + ArrowLeft + Space.
3. Exercise 3 — Fast two-letter overlap simulation: Hold ShiftLeft with your left pinky, hold KeyT with your left index finger, and tap KeyH and KeyE without releasing KeyT. In rapid touch typing at 90+ WPM, the next finger frequently closes its switch 15 ms to 30 ms before the previous finger finishes lifting. If holding ShiftLeft + KeyT blocks KeyE, capitalized words like The or There will drop their vowel whenever you type briskly.
4. Exercise 4 — Wired vs. wireless mode comparison: If you own a tri-mode keyboard (USB-C wired, 2.4 GHz dongle, and Bluetooth), run the 8-finger home-row press in each connection mode and click reset test between runs. Many boards deliver 10+ key NKRO over USB-C and 2.4 GHz, but cap reports at 6 keys when connected over Bluetooth.

If your max simultaneous score is lower than your keyboard's specification sheet claims, check these three hardware and firmware settings:

• Hardware NKRO toggle is switched off: Many mechanical keyboards boot in 6-key mode so older motherboard BIOS screens can read them. Check your manual for the NKRO hotkey (often Fn + N, Fn + ScrLk, or Left Shift + Right Shift + N in QMK).For the electrical circuit explanation of matrix diodes and USB packet bytes, read our guide on what key rollover and ghosting mean.
• Individual switch is failing to close: If one specific key never appears in your chord, release all other keys and press that key alone. If it still fails or flickers, inspect it on the full-layout keyboard tester and follow how to test your keyboard for stuck keys.
• Switch is bouncing instead of holding steady: If a held key flickers in and out of the live list while your finger keeps steady pressure on the cap, the internal contact leaf is oxidized or loose. Measure its bounce intervals on the key chatter test. To benchmark your typing speed or check scoring math, visit the typing test and the WPM calculator.