Keyboard Tester
A free tool to visually test for broken keys
and verify N-key rollover capabilities.
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About Keyboard Tester
The Keyboard Tester is a free, browser-based utility that lets you verify the functionality of every key on your keyboard.
It supports switching between Windows and Mac modifiers, as well as JIS (Japanese) and US layouts. The on-screen virtual keyboard provides real-time visual feedback of your keystrokes. This is incredibly useful for checking a newly purchased keyboard for dead keys, verifying functionality after a liquid spill, or testing the limits of N-key rollover for gaming.
Because the tool operates entirely on the client side (in your browser), your keystrokes are never transmitted to any external servers, guaranteeing your privacy and security.
How to Use
Configure Environment
Select your operating system (Windows / Mac) and keyboard layout (JIS / US) from the top settings area. The virtual keyboard will instantly adapt to your choice.
Test Key Presses
Press the keys on your physical keyboard one by one. Keys that register correctly will light up and be marked as 'tested' on the screen.
Check Results and Reset
Ensure no key is left untested. You can also press multiple keys at once to measure the N-key rollover capability. Use the "Reset History" button to start a new test.
Keyboard Glossary
- JIS / US Layout
- The JIS (Japanese Industrial Standard) layout features a large L-shaped Enter key and specific keys for Japanese input. The US layout is the standard for English-speaking regions, characterized by a horizontal Enter key and a wider Space bar, often preferred by programmers.
- N-Key Rollover (NKRO)
- The ability of a keyboard to correctly register all keystrokes even when multiple keys are pressed simultaneously. The 'N' stands for 'any number', meaning theoretically every key can be pressed at once. This is a critical feature for gaming keyboards.
- Anti-Ghosting
- A feature that prevents the 'ghosting' effect, where an extra, unpressed key is erroneously registered when multiple keys are pressed simultaneously. It works hand-in-hand with N-key rollover.
- Key Chattering
- A hardware issue, particularly common in mechanical keyboards, where a single physical press results in multiple character inputs (e.g., typing 'hhello' instead of 'hello') due to electrical contact bouncing.
- event.code
- A property of browser JavaScript events that represents the physical key pressed on the keyboard, independent of the keyboard's layout mapping or the character produced (event.key). This tool uses this property to accurately track physical keystrokes.
Frequently Asked Questions
- Q.Is there any risk of my passwords or keystrokes being leaked?
- No, there is no risk. This tool runs entirely on your browser using JavaScript. Keystroke data is never sent to any external servers, ensuring complete privacy.
- Q.The 'Fn' or 'PrtScn' keys do not respond.
- Keys like 'Fn' on laptops are handled at the hardware level and are not sent to the browser as key codes, so they cannot be tested. Also, system shortcuts like 'PrtScn' or 'Ctrl+W' may be intercepted by the OS or browser and may not respond.
- Q.Can I use this on a smartphone or tablet software keyboard?
- This tool is designed specifically for testing physical hardware keyboards. Software keyboards (touchscreen input) on smartphones do not send physical key codes, so they cannot be tested properly.
- Q.Is there a limit to measuring N-key rollover?
- The tool itself has no limit, but the maximum number of simultaneous keys recognized depends on your keyboard's hardware specifications and connection type (USB or Bluetooth). Standard USB keyboards often limit recognition to 6 simultaneous keys.
- Q.On Mac, pressing the Command key triggers a system shortcut.
- System-level shortcuts (like Cmd+Tab or Cmd+Q) override browser controls and cannot be blocked by the tool. Please test modifier keys individually to avoid triggering shortcuts.
Use Cases
Testing New Keyboards
Quickly check for any dead keys or manufacturing defects right out of the box by pressing every key systematically.
Gaming Setup Verification
Test the limits of your keyboard's N-key rollover capability, essential for FPS or rhythm games that require complex simultaneous inputs.
Post-Spill Diagnostics
After accidentally spilling a drink or performing a deep clean, verify that all switches and electrical contacts are still functioning correctly.
Custom Build Testing
For custom mechanical keyboard enthusiasts, test matrix wiring and switch actuation immediately after soldering or assembly.
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