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Key Rollover Tester (N-Key Rollover / Anti-Ghosting)

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Keyboard Checker

Check which keys on your keyboard are working with a clear visual pass/fail grid.

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Key rollover (or NKRO - N-Key Rollover) measures how many keys your keyboard can register accurately when pressed at the same time, which matters most for gaming combos and fast typing where several keys overlap. This tester shows a live count of currently held keys, the active key combination, and tracks the maximum simultaneous rollover you've achieved during the session, so you can identify 'ghosting' - where pressing a specific combination of keys causes one to silently fail to register, or a phantom key to appear. Try common combinations (WASD plus Shift, or several letter keys together) to see how your keyboard's rollover actually behaves under real multi-key pressure, not just spec-sheet claims.

Features

  • ✓Live count of simultaneously held keys
  • ✓Displays the exact active key combination
  • ✓Tracks maximum rollover achieved during the session
  • ✓Full keyboard diagram for visual confirmation
  • ✓Useful for verifying NKRO/anti-ghosting marketing claims

Why use this key rollover tester?

  • Instant results with no page reloads or server round trips
  • 100% private - everything runs locally in your browser, nothing is uploaded
  • Reveals real-world rollover behavior, not just spec-sheet numbers
  • Completely free with no signup, installs, or usage limits

Frequently asked questions

What is key rollover / NKRO?

Key rollover is the number of keys a keyboard can register correctly when held down at the same time; N-Key Rollover (NKRO) means, in principle, unlimited simultaneous keys, versus common budget boards that support only 2-6.

What is 'ghosting'?

Ghosting happens when a specific combination of simultaneously pressed keys causes one or more of them to fail to register, or an unintended extra key to appear to be pressed - a limitation of the keyboard's internal key matrix.

How do I test for ghosting with this tool?

Hold combinations of 3+ keys at once (especially keys close together on the same rows/columns) and watch whether the active combination shown matches exactly what you're pressing.

Can browser-based testing measure true NKRO accurately?

Browsers can only report what the OS and keyboard driver already deliver, so this test reflects real-world browser-level rollover behavior, though extremely high rollover keyboards may be limited by USB/OS reporting in some setups.