Level A · WCAG 2.0
2.3.1 Three Flashes or Below Threshold
Nothing flashes more than three times per second.
Manual only No automated check says anything useful.
How it fails in practice
A celebratory confetti animation at checkout with rapid high-contrast strobing. This criterion exists because the failure can trigger a seizure.
How to fix it
Keep flashes under three per second, or remove the effect. Treat it as a safety requirement, not a style question.
At a glance
- Level
- Level A — the minimum. Failing one of these usually makes something impossible rather than merely hard.
- Principle
- Operable
- Guideline
- 2.3 Seizures
- Added in
- WCAG 2.0
- EN 301 549
- 9.2.3.1
- Automated check
- Manual only
Manual only
How far an automated check gets
Nothing automatic decides this. A scanner that reports it as passing is reporting that it did not look. It stays untested until a person tests it and records what they did — which is exactly how we treat it: as untested, not as passed.
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