Free Online Keyboard Tester

What This Keyboard Tester Does

This tool intercepts keyboard events at the browser level using the DOM's addEventListener('keydown') and addEventListener('keyup') APIs. Every key press sends an event containing the key's logical name (KeyboardEvent.key), physical position code (KeyboardEvent.code), and legacy numeric keyCode. The virtual ANSI/ISO keyboard layout on screen highlights pressed keys in real time — cyan while held, green once released — giving immediate visual confirmation of which keys the OS and browser actually registered.

Keyboard Rollover Comparison — 2KRO vs. 6KRO vs. NKRO

N-key rollover (NKRO) means every key on the keyboard is scanned independently, so any number of keys pressed simultaneously are all correctly registered. Most keyboards fall into one of three categories:

To test your keyboard's actual rollover: press and hold 7+ keys simultaneously above and watch which ones light up. Any key that fails to register reveals your actual rollover limit — regardless of what the marketing spec claims.

Who Uses a Keyboard Tester

How to Test Your Keyboard

1. Click in the test area. Click the keyboard display area to ensure keyboard events go to the tester, not the browser address bar or other inputs.
2. Press every key individually. Work systematically: number row, top letter row, home row, bottom row, then modifiers, function keys, and numpad.
3. Watch for green highlights. Each key should turn green after you press and release it. Any key that doesn't highlight is unresponsive.
4. Test multi-key rollover. Press 6–10 keys simultaneously and verify all of them light up. Drop-outs indicate ghosting.
5. Check key codes. The sidebar shows the KeyboardEvent.key, code, and keyCode for each press — useful for developers debugging key bindings.

Keyboard Switch Types and How They Affect Testing

Limitations of the Browser Keyboard Tester

Frequently Asked Questions

How does this keyboard test work?

The tool listens to browser DOM keyboard events: keydown fires when a key is pressed, and keyup fires when it is released. Each event contains the key's KeyboardEvent.key (the logical key name), KeyboardEvent.code (the physical key code based on position), and KeyboardEvent.keyCode (the legacy numeric code). The virtual keyboard layout on screen highlights the corresponding key in cyan while held and marks it green once released, confirming it was registered.

What is keyboard ghosting?

Keyboard ghosting occurs when pressing multiple keys simultaneously causes the keyboard controller to fail to register all of them, or to register extra phantom keys that weren't pressed. This happens because many budget keyboards share electrical columns and rows in their matrix design — pressing three keys that form a circuit rectangle on the matrix confuses the controller. Anti-ghosting and N-key rollover (NKRO) keyboards solve this by using diodes or USB HID polling that reports each key individually.

Why doesn't the Fn (Function) key light up?

The Fn key on most laptops is handled directly by the hardware or embedded controller (EC) firmware, not the operating system. It doesn't generate standard OS-level keyboard scan codes and therefore doesn't produce a keydown or keyup event that the browser can see. This is a hardware-level design decision — Fn modifies hardware behavior (brightness, volume, etc.) without involving the OS or browser.

What is N-key rollover (NKRO) and how do I test it?

N-key rollover means every key on the keyboard is scanned independently, so any number of keys pressed simultaneously are all correctly registered. To test it with this tool, press as many keys as you can simultaneously and check whether every key you're pressing lights up on the virtual keyboard. If some keys don't register when held with others, your keyboard has limited rollover. Most gaming mechanical keyboards over USB support 6-key rollover or full NKRO.

Does it test Windows, Mac, and Chromebook layouts?

The virtual keyboard displays standard ANSI and ISO layouts covering all common key positions. Mac-specific keys (Command ⌘, Option ⌥) and Windows keys (Win key, Menu) all generate keyboard events and will highlight on the virtual layout. Chromebook-specific keys like Search/Launcher generate similar events to the Win key. Special Mac-only key combinations that are handled at the OS level before reaching the browser (like Command-Tab) may not register.

Can I test if my keyboard has key chatter or double-typing?

Yes. Quickly tap a single key once and watch the event counter. If you see multiple keydown events from a single physical press, your switch is chattering. Chatter is common in worn mechanical switches, where the electrical contact bounces briefly on actuation, sending multiple signals. This causes double letters when typing. You can detect this in the tool by pressing a key quickly and checking if it registers multiple separate key events.

Why do some keys show different codes on Windows vs. Mac?

The KeyboardEvent.code property (which reflects physical key position) is consistent across operating systems for standard keys. However, KeyboardEvent.key (the logical meaning) can differ — the Windows key produces'Meta' on Windows, the Command key produces'Meta' on Mac, but they have different key positions. Some special keys (like PrintScreen, which doesn't exist on Mac) simply don't generate events on platforms where they're absent.

Can this diagnose a water-damaged or liquid-damaged keyboard?

Partially. If liquid damage caused individual switch failures, those keys won't register when pressed — a clear sign in the tester. However, liquid damage can also cause bridges between key matrix rows, which creates ghost key events (keys registering that weren't pressed). If you see random keys lighting up without pressing them, liquid bridge damage is a likely cause alongside other possibilities like ESD or a faulty keyboard controller.

Does this work with external USB keyboards and wireless keyboards?

Yes. The keyboard tester works with any keyboard that registers as a standard HID (Human Interface Device) with the operating system — including USB wired keyboards, USB wireless receivers, and Bluetooth keyboards. As long as the key events reach the OS and then the browser, they will be detected. Some specialized keys on multimedia keyboards (volume slider, custom macro keys) may use different HID protocols that browsers don't see.

What is the difference between KeyboardEvent.key and KeyboardEvent.code?

KeyboardEvent.key is the logical value of the key based on the current keyboard layout. For example, on a French AZERTY keyboard, pressing the key in the Q position returns'A'. KeyboardEvent.code is the physical key code based on position on a standard US QWERTY keyboard — the same physical key always returns'KeyQ' regardless of layout. code is useful for games where physical position matters; key is useful for text input where the logical character matters.

What is a good keyboard ghosting test?

To test for keyboard ghosting: (1) Open this keyboard tester, (2) Hold down the W, A, S, D keys simultaneously (the standard gaming movement cluster), then add Shift, Space, and Ctrl one at a time. A keyboard with ghosting will fail to register one or more of these keys when all are held. Repeat with the Q, E, R, T, F, G, H row — these are classic matrix rectangles that trigger ghosting on budget keyboards. Every key that lights up on the virtual keyboard is registered; any key that stays dark despite being pressed has been ghosted by the keyboard's matrix design.

How do I know if my keyboard supports N-key rollover (NKRO)?

Press 7 or more keys simultaneously on this tester. If all 7+ keys highlight on the virtual keyboard at the same time, your keyboard supports at least 7-key rollover or full NKRO. If some keys don't register when held with others, you've hit the rollover limit. Most keyboards marketed as 'N-key rollover' over USB use a special HID report format — some require enabling NKRO mode via a specific key combination (consult your keyboard's manual). Note: PS/2 keyboards support true NKRO by hardware protocol; most USB keyboards support 6KRO by default.