Keyboard Test and Key Rollover Check
Press any physical key or tap the on-screen key map to verify keydown and keyup events and check for ghosting when holding three or more non-modifier keys.
Ready
How it works
This tool listens to standard browser keyboard events as they reach your active window. When you press a key, the browser fires a keydown event and highlights the matching position on the visual key map. When you release the key, a keyup event fires and updates the key to a tested state. If you hold down three or more non-modifier keys at the same time, the tool shows a ghosting hint so you can see whether your keyboard matrix drops or blocks additional simultaneous presses. Phones and tablets without a physical keyboard can tap the visual map directly.
Steps
Step 1: Click or tap inside the test area to make sure the browser window has active input focus. Step 2: Press keys one by one across your physical keyboard, or tap keys on the on-screen map on a phone, watching each key light up on keydown and settle on keyup. Step 3: Hold three or more non-modifier keys together to trigger the ghosting hint and verify multi-key rollover.
Controls
The visual key map displays active keys during a keydown event and marks keys that have completed a full keyup cycle. On-screen readouts show the most recent key code, the current count of simultaneously held keys, and the peak simultaneous key count recorded during your session. A ghosting hint appears whenever three or more non-modifier keys are held down together, and a reset button clears the map.
Examples
Example 1: You press and release the W, A, S, and D keys one at a time. Each key highlights on keydown and stays marked after keyup, showing normal single-key registration. Example 2: You hold W, E, and R together, and the ghosting hint appears while all three keys highlight, confirming 3-key support on that cluster. Example 3: You hold A, S, D, and F, but F never highlights on the map, indicating matrix blocking on that fourth non-modifier key.
How to read your result
Use the highlighted map and active key counter as a practical check of what your operating system and browser receive from your hardware. If a single key fails to highlight on keydown or stays stuck on the map after you release it, the switch, contact, or OS key binding may need attention. If holding three or more non-modifier keys stops new keys from registering, you are seeing hardware rollover limits rather than a software error. These results are a basic hardware check, not a formal diagnosis.
Reference ranges
These rough comparison bands describe common hardware behavior and are not a medical, psychological, or clinical scale. Many basic office and laptop membrane keyboards register around 2 to 3 simultaneous non-modifier keys on shared matrix paths before blocking additional keys. Many gaming membrane keyboards handle around 6 simultaneous keys across common movement clusters. Mechanical and hall-effect keyboards with full N-key rollover over USB typically register 6 or more non-modifier keys at once, often up to the limits of the USB report mode or browser focus.
Tips
On a desktop or laptop, click inside the page before typing, and avoid pressing system shortcuts like Ctrl+W, Alt+F4, or Command+Q that close or switch browser tabs. Test specific key clusters you actually use in games or daily work, since matrix blocking varies by row and column. On a phone or tablet, connect a Bluetooth or USB keyboard to test physical switches, or tap the on-screen key map directly to verify layout responsiveness.
FAQ
What does this keyboard test measure and what does it not claim?
This tool measures whether standard browser keydown and keyup events reach the page, tracks how many keys are held at once, and flags a ghosting hint at three or more non-modifier keys. It does not measure physical actuation force, switch travel distance, or electrical debounce timing inside the keyboard controller.
Why can two runs on the same keyboard show different rollover counts?
Most membrane keyboards wire keys in a row-and-column grid. Holding three non-modifier keys in one corner of the grid may trigger matrix blocking at three keys, while holding keys on separate rows and columns can allow four to six keys to register cleanly on the exact same keyboard.
How do I run this test on a phone or tablet?
If you are using a phone or tablet without an external keyboard attached, you can tap the keys directly on the on-screen key map to trigger press states. If you pair a Bluetooth keyboard or plug in a USB keyboard, press its physical keys just as you would on a desktop.
Where are my test results and key presses stored?
Everything stays in your browser on this device only. Your key presses and test results are never collected or uploaded to any server. High scores or peak simultaneous key counts may be saved in your browser's local storage on this device so you can compare runs later.
What do a high multi-key count and a low count usually mean?
A high simultaneous key count usually means your keyboard uses diodes on each switch or supports multi-key rollover across the tested cluster. A low count around two or three non-modifier keys usually reflects standard membrane matrix limits. This reflects keyboard wiring only and is not a health or psychological diagnosis.
Privacy
This page runs entirely in your browser on this device; your key presses and results are never collected or uploaded, though peak scores may be kept in local storage on this device.