Keyboard Tester & Key Ghosting Diagnostic Online Free
Press physical keys and watch them light green on a virtual main keyboard and numpad. Live telemetry shows key, code, keyCode, location and repeat; a coverage percentage tracks how many of the mapped keys have fired at least once. Hold several keys together to probe ghosting (dropped simultaneous events). Reset clears the board. Ideal for dead-key hunts, laptop repairs, mechanical switch QA and “which key is this” debugging — key contents never leave your browser.
Keyboard Tester & Key Ghosting Diagnostic In-Browser Workspace
Input data or select files to begin. 100% private, client-side execution with zero server transmission.
How to Use Keyboard Tester & Key Ghosting Diagnostic
- Step 1: Click into the page so key events reach the window listeners.
- Step 2: Press keys — the matching virtual key flashes amber then stays green.
- Step 3: Watch coverage climb toward 100% across main and numpad tabs.
- Step 4: Hold chords like A+S+D+F to see if any key fails to report (ghosting).
- Step 5: Use Reset to clear tested state when starting a new keyboard.
About Keyboard Tester & Key Ghosting Diagnostic
Browsers deliver KeyboardEvent with a physical layout-independent code (KeyA, Digit1, ShiftLeft) plus a layout-dependent key string. The tester listens on window keydown/keyup, preventDefaults so Space/Tab do not scroll or leave the page, and inserts e.code into a Set for permanent “tested” marks. keyCode/which is included for legacy compatibility even though it is deprecated. Coverage = tested.size / total mapped codes × 100. Ghosting arises in cheap membrane matrices that cannot distinguish every combination of closed switches — N-key rollover (NKRO) boards and higher-quality membranes report all chords; the UI encourages multi-key holds to reveal drops. Numpad codes (Numpad0–9, operators, NumLock) are on a second tab because many laptop keyboards omit them. Browser-level shortcuts (Alt+Tab, Cmd+Q) may still be swallowed by the OS before page handlers run — that is environment behavior, not a dead key. No key values are stored or transmitted; only local React state tracks the Set.
Frequently Asked Questions
Why do some keys still navigate the page?
F1, F5, browser shortcuts and Alt/Cmd combos can be reserved by the browser or OS before the page sees them.
What is key code vs key string?
code is physical position (KeyQ); key is the character produced (q or Q depending on shift/layout). Both are shown.
Is ghosting my keyboard or the browser?
If several simultaneous keys never fire keydown while single presses work, it is usually matrix ghosting/rollover hardware limits.
Are key presses logged or uploaded?
No — state is in-memory only for the session; nothing is sent to a server.
Does it work on phones?
Touch keyboards send limited codes; the tool is designed for hardware USB/Bluetooth keyboards.