Keyboard Tester
Press any key to test it. Every key lights up on the visual keyboard. Check keycodes, test N-key rollover, see your typing heatmap, and detect stuck keys.
N-Key Rollover Test
Press and hold multiple keys simultaneously. All detected keys appear below. If a key you're pressing doesn't show up, your keyboard is ghosting that combination.
Key History
Last 20 key presses with timestamps, most recent first.
| # | Key | Code | keyCode | Time |
|---|---|---|---|---|
| No keys pressed yet | ||||
How to Use This Keyboard Tester
- Test individual keys: Press any key and watch it light up on the visual keyboard. The info panel shows the key name, code, keyCode, and physical location (left, right, numpad, or standard).
- Check for broken keys: Press every key one by one. The "Unique Keys" counter tracks how many distinct keys you've tested. Aim to match your keyboard's total key count.
- Test N-key rollover: Hold multiple keys at once (try WASD + Shift + Space). The rollover panel shows every key the computer detects simultaneously. Missing keys mean ghosting.
- Read the heatmap: As you type, keys shift from blue (few presses) through yellow to red (many presses), showing your most-used keys at a glance.
- Detect stuck keys: If any key stays held for over 3 seconds, a warning banner appears. This helps identify physically stuck switches or software-level repeat issues.
Keyboard Rollover Benchmarks
How many simultaneous key presses does your keyboard support? Here's what to expect from different keyboard types.
| Keyboard Type | Typical Rollover | Notes |
|---|---|---|
| Budget Membrane | 2-3 KRO | Most basic keyboards. May ghost with 3+ keys held. Fine for typing, problematic for gaming. |
| Laptop Built-in | 3-4 KRO | Varies widely by model. Gaming laptops often support 5-6 KRO on WASD clusters. |
| Gaming Membrane | 6 KRO (anti-ghosting zones) | Enhanced matrix in WASD/gaming zones. Full rollover in other areas may be limited. |
| Mechanical (USB) | 6 KRO / Full NKRO | USB protocol defaults to 6KRO. Most support full NKRO mode via firmware toggle. |
| Mechanical (PS/2) | Full NKRO | PS/2 protocol natively supports unlimited simultaneous keys. Rare on modern boards. |
Common Key Codes Reference
Quick reference for commonly used JavaScript key codes and their corresponding values.
| Key | keyCode | code | key value |
|---|---|---|---|
| Enter | 13 | Enter | Enter |
| Space | 32 | Space | " " (space) |
| Escape | 27 | Escape | Escape |
| Tab | 9 | Tab | Tab |
| Shift (Left) | 16 | ShiftLeft | Shift |
| Ctrl (Left) | 17 | ControlLeft | Control |
| Alt (Left) | 18 | AltLeft | Alt |
| Arrow Up | 38 | ArrowUp | ArrowUp |
| Arrow Down | 40 | ArrowDown | ArrowDown |
| A | 65 | KeyA | a |
| 0 | 48 | Digit0 | 0 |
| F1 | 112 | F1 | F1 |
Frequently Asked Questions
What is a keyboard tester and why should I use one?
A keyboard tester is an online tool that detects and displays every key press on a visual keyboard layout. It helps you verify that all keys on your keyboard are working correctly, which is especially useful when buying a used keyboard, troubleshooting unresponsive keys, or testing a new mechanical keyboard. This tool shows the keycode, key name, and location for each press, plus tracks your typing heatmap and tests N-key rollover.
What is N-key rollover (NKRO) and why does it matter?
N-key rollover (NKRO) refers to how many keys your keyboard can register simultaneously. A keyboard with full NKRO can detect every key pressed at the same time, no matter how many that is. This matters for gaming, where you might press W + A + Shift + Space + Ctrl simultaneously. Cheaper membrane keyboards often only support 2-3 key rollover (called 2KRO or 3KRO), meaning extra simultaneous presses get dropped — this is called 'ghosting'. Most mechanical keyboards support 6KRO over USB or full NKRO.
Why are some of my keys not registering?
If keys aren't registering in this tester, there are several possible causes: 1) Your keyboard has limited rollover — try pressing fewer keys simultaneously. 2) The key switch is physically broken or has debris underneath — try removing the keycap and cleaning it. 3) Your keyboard's USB connection is intermittent — try a different port or cable. 4) Software conflicts — some keyboards have Fn-lock modes or driver issues. 5) Browser limitations — certain key combinations (like Ctrl+W) are intercepted by the browser before they reach the page.
What are keycodes and why do different keyboards show different values?
Keycodes are numeric identifiers the browser assigns to each key press. The 'key' property gives the readable character (like 'a' or 'Enter'), while 'keyCode' gives the legacy numeric code (like 65 for 'A'). The 'code' property identifies the physical key location (like 'KeyA') regardless of keyboard layout. Different keyboards may show different values because of layout differences (QWERTY vs AZERTY vs Dvorak), regional variations, or custom firmware that remaps keys.
How does the typing heatmap work?
The typing heatmap color-codes each key based on how many times you've pressed it during your current session. Keys you haven't pressed stay their default color. As you press keys more frequently, they shift from blue (cool, few presses) through yellow to red (hot, many presses). This visualization helps you understand your typing patterns, identify which keys you use most, and can be useful for optimizing custom keybind layouts in games.
Can this tool detect if a key is stuck?
Yes. This keyboard tester includes a stuck key detector that monitors how long each key is held down. If a key appears to be held for more than 3 seconds without being released, a warning will appear. Stuck keys can be caused by physical debris under the switch, a broken spring in a mechanical switch, liquid damage, or software-level key repeat issues. If you see a stuck key warning, try pressing the key firmly to unstick it, or remove the keycap to inspect the switch.
Does this keyboard tester work with any keyboard layout?
This tool works with any keyboard that connects to your computer, including QWERTY, AZERTY, Dvorak, and other layouts. The visual keyboard shows a standard US QWERTY layout for reference, but key detection works regardless of your physical layout. The 'code' value shown for each press identifies the physical key position, while the 'key' value shows the character your OS maps to that position. This means the highlighted key on the visual layout always matches the physical position you pressed.