| What it does | Measure anything on your screen with pixel-perfect accuracy
| Test your visual reaction time for free
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| Stage | Not given
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| Pricing model | Free
| Free
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| Pricing | Not given
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| Key features | - Smart Auto-Detect identifies your device from a database of 100+ profiles
- Three calibration methods: auto-detect, screen diagonal, and credit card
- Place rulers on any edge of the screen in any combination
- Click-to-measure distances in any direction
- Live cursor position tracking
- Dark mode with automatic system preference detection
- Support for four measurement units: cm, mm, inches, and pixels
| - Five-round visual reaction test with millisecond timing
- Seven-round sound reaction time test
- Local result history with up to 300 sessions stored
- Consistency measurement showing standard deviation of scores
- Download score card as image
- Sound calibration for personal offset adjustment
- Reference data from published research studies
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| What makes it different | - No installation required—runs entirely in your web browser
- Achieves near pixel-perfect accuracy typically within 0.5mm for well-calibrated screens
- Completely free with no ads, account, or limitations
- Calibration saved locally so no need to recalibrate on each visit
- Works on tablets and mobile devices with touchscreen support
| - No account or login required to use the test
- Results stored locally in browser for privacy
- Compare full sessions to understand consistency, not just fastest round
- Research-backed reference data from laboratory studies
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| Free plan | Not given
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| Open source | Not given
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| Platforms | Not given
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| Public API | Not given
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| Community votes | 0 | 0 |
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| DR (Domain Rating by Ahrefs) | 1 ● no change since last check | 3 ● no change since last check |
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| Trust Flow (Majestic) | 0 | 0 |
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| Citation Flow (Majestic) | 17 | 11 |
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| Referring domains (Majestic) | 4 | 1 |
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Online Ruler
ReactionTests