Test every key on your keyboard online. Check stuck keys, missed inputs, key rollover and key codes directly in your browser.
KeyboardEvent.code
Testing Full Size (104-Key ANSI). Press keys to watch them light up, check matrix contacts, and verify layout response.
Hold multiple keys at once to measure browser-visible simultaneous rollover. Standard office keyboards typically block after 3 to 6 simultaneous presses (6KRO), while gaming keyboards with dedicated diodes register unlimited simultaneous keys (NKRO).
Oxidation or dust on mechanical switch leaves can cause rapid micro-bounces. Use compressed air or electronic contact cleaner to clear debris.
If a key remains highlighted after release, it indicates either mechanical sticking or that the operating system intercepted the keyup event.
Some laptop Fn keys and specialized media shortcuts are handled internally by motherboard hardware and never send browser events.
Web browsers receive keystrokes through low-level DOM event streams (keydown, keyup). By capturing events at the window capture phase, the tester prevents default actions (such as Space scrolling and Tab focus jumps) while isolating switch conduction.
The property event.code represents the physical position of a key switch on the circuit board (e.g., "KeyQ"), whereas event.key represents the active character interpretation (e.g., "q" on QWERTY or "a" on AZERTY). Mapping physical codes ensures international layout accuracy.
Membrane keyboards connect key switches in a matrix grid of X and Y circuit traces. Pressing certain three-key combinations forms a closed loop that can cause ghosting. Anti-ghosting designs add isolation diodes to ensure each switch path remains electrically independent.
When physical mechanical switch contacts collide, metal leaves bounce for 1 to 5 milliseconds before settling. Firmware debounce algorithms filter out these micro-oscillations. When contacts corrode, chatter exceeds debounce thresholds and produces unintended double-typing.
Standard USB HID keyboards historically sent 6-byte key reports (6KRO plus modifiers). Modern gaming keyboards use custom USB report descriptors or multiple logical endpoints to achieve true N-Key Rollover (NKRO), registering unlimited simultaneous key activations.
Online rollover tests measure the number of simultaneous key events that successfully pass through the keyboard controller, USB stack, operating system, and browser thread. It measures practical application-level rollover rather than theoretical raw switch scan rates.
Membrane switches rely on pressure domes closing carbon contacts; mechanical switches use moving stems and metal leaves; optical and magnetic Hall-effect switches use light beams and magnetic flux. The tester evaluates electrical event arrival regardless of switch technology.
Certain critical system key combinations (such as Ctrl+Alt+Del, Alt+Tab, Cmd+Tab, or browser-reserved Ctrl+W) are intercepted by the operating system kernel before reaching web pages. Missing events for these shortcuts reflect OS design, not hardware switch defects.
Modifier states like Caps Lock, Num Lock, and Scroll Lock are tracked by the operating system. Modern web browsers expose these states via the getModifierState() API, allowing the tester to verify physical LED toggle states in real time.
Laptop scissor switches use thin silicone membranes that are vulnerable to dust and dried liquid residue. Cleaning under keycaps with short bursts of compressed air often restores unresponsive membrane contacts without replacing the keyboard assembly.
Wireless keyboards operating on the 2.4GHz spectrum can suffer packet loss due to Wi-Fi router interference or low battery voltage. Dropped keystrokes or delayed keyup events often resolve by moving the USB receiver closer or replacing batteries.
Keystroke data is sensitive. EasyToolio processes all keydown, keyup, and rollover telemetry entirely within your local browser memory space. No keystroke logging, string assembly, or remote telemetry is ever transmitted.
Quick answers about how this tool works.
Plain-language explainers that sit next to this tool.
Before you hand over cash for a second-hand laptop, run it through these six free browser tests to catch hidden hardware wear.
Understand how stylus pressure sensitivity actually works via the Pointer Events API, the most common causes of broken pressure response, and how to isolate a driver issue from an app setting.
Learn how headphone left/right channel reversal happens, why casual listening often misses it, and how a simple left-only then right-only test tone sequence makes it obvious.
Your mouse box says 1000Hz, but a browser-based test might show something different — here is why observed polling rate and advertised hardware polling rate are not quite the same measurement.
Be the first to rate Keyboard Tester
Search 250+ free tools by name, or pick a category below. Every one runs instantly in your browser — no signup, nothing to install.
Tap a star to rate Keyboard Tester.