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Keyboard tester troubleshooting: find stuck keys and ghosting fast

Use a repeatable checklist to identify hardware issues, switch problems, and rollover limits in minutes.

7 min read Jan 12, 2026 Updated Jan 17, 2026
Diagnostics Hardware Rollover

The keyboard tester lets you confirm every key press in real time. Use a consistent checklist so you can isolate the problem fast instead of guessing.

1. Match the layout and connection

Choose the layout that matches your physical keyboard. If you are on a wireless board, verify the receiver or Bluetooth connection first.

  • Pick the correct layout (QWERTY, AZERTY, QWERTZ, and so on).
  • Unplug and reconnect if the board is not fully recognized.
  • Avoid hubs if the keyboard is dropping inputs.
Keyboard tester interface showing layout selection and the virtual keyboard.
Match the on-screen layout to your physical keyboard before testing.

2. Run a baseline pass

Press every key once from left to right. Missing highlights can signal a stuck switch or a layout mismatch.

Tip: If a key stays lit after you release it, it is likely stuck or repeating.

3. Test rollover and ghosting

Hold two or three keys and press a fourth. If the tester stops registering, your keyboard may have a rollover limit.

Test What to look for Likely cause
ASD + Space Space does not register Limited rollover
Shift + W + D One key drops Ghosting on matrix
Ctrl + Alt + Del Inconsistent combo Driver or layout issue
Keyboard tester with multiple keys highlighted to demonstrate rollover testing.
Hold multiple keys to reveal rollover limits and ghosting.

4. Check modifiers and layers

Press Shift, Ctrl, and Alt with regular keys. If modifiers fail, test on another browser or confirm no remapping is active.

Some Fn layers are handled in hardware and will not show in the tester, so focus on standard modifiers and alphanumeric keys.

5. Rule out software issues

Open the tester in another browser or a private window. If the problem disappears, it may be caused by extensions or input remapping software.

  • Disable key remaps or macro tools temporarily.
  • Check OS-level accessibility settings.
  • Test the same key on a second device if possible.

6. Document and decide next steps

Take a screenshot, clean the keyboard, and retest. If the same key fails again, it is likely hardware related.

Fast checklist

  • Match the layout first
  • Press every key once
  • Test 3-4 key combos
  • Check modifiers
  • Retest after cleaning

Next steps

If the issue repeats, test on a second device or replace the switch.

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