FAQ
Answers to common questions about photosensitive epilepsy, WCAG 2.3.1 compliance, and using Video Audit.
Who should use this tool and why?
Video creators, developers, and accessibility specialists should use this tool to test animations and videos for photosensitive epilepsy triggers. This includes video creators, editors, web and game developers, and accessibility specialists. For example, web developers can use it to test animated banners or game scenes, and video producers can check their film or ads for safety. WCAG explicitly notes that all content on a webpage must meet seizure-safety criteria w3.org. Our video analysis tool serves the same audience: if your website or video might have flashing content, it’s wise to check it.
Is there a free online epilepsy test for videos and GIFs?
Yes, video-audit.com is a completely free, browser-based photosensitive epilepsy safety scanner for videos and GIFs. You do not need to download or install any native desktop software to check your clips. Simply drag and drop your `MP4`, `WebM`, or `MOV` file into our analyzer to instantly test for photosensitive epilepsy risks directly in your web browser.
Is this tool officially recognized by the W3C?
Yes, this tool is listed on the official W3C WAI Evaluation Tools List for verifying WCAG 2.3.1 compliance. It is designed to test specifically for WCAG Success Criterion 2.3.1 regarding flashing content.
What is the Harding test and how does this tool compare?
The Harding FPA is a paid, broadcast-industry software mandated by Ofcom, whereas our tool is a free, web-based WCAG 2.3.1 checker. It is a highly sophisticated, technical piece of paid software designed primarily for professional TV production. While our tool uses similar underlying mathematical concepts (analyzing luminance/red transitions) to detect flashing, we are a free, simplified, web-based tool focused squarely on WCAG 2.3.1 compliance for digital web creators. We are not officially affiliated with the Harding Test.
How do I test my video or website for seizure-triggering flashes?
To test a website or video, simply upload a screen recording or video file directly to our browser-based analyzer. Simply record the content (e.g. using screen-capture software) and upload that video to our tool. The system will analyze it frame by frame.
How do I interpret the analysis charts and warnings?
The analysis charts display relative luminance shifts and red ratios, with warning flags highlighting any WCAG flash violations. Spikes in the luminance chart (usually a white line) indicate bright flashes or transitions; spikes in the red-ratio chart indicate frames where the scene is very red. Above each spike, the tool flags whether it constitutes a WCAG “general flash” or “red flash”. Flashes that occur more than three times per second are considered WCAG violations and listed in warning boxes below the charts.
What should I do if my video violates the flash guidelines?
If your video violates the guidelines, you must edit the content to lower flash frequency, contrast, or saturated red areas. Common fixes include:
- Reduce Flash Rate: Edit the video so flashing scenes occur at ≤3 times per second or break them into slower sequences.
- Lower Brightness/Contrast: Tone down sudden brightness jumps (so luminance changes are less than 10%).
- Avoid Intense Reds: Recolor saturated reds to less intense hues or desaturate them.
- Minimize Flash Area: Crop or mask large bright areas, so simultaneous flashes cover less than ~25% of the screen.
What is photosensitive epilepsy and what triggers it?
Photosensitive epilepsy is a neurological condition where seizures are triggered by flashing lights or high-contrast visual patterns. In other words, rapid light/dark changes can induce seizures in susceptible people (epilepsy.org.uk, developer.mozilla.org).
How do flashing lights in videos affect people with this condition?
Flashing lights in videos can induce seizures, migraines, or dizziness in photosensitive viewers by overstimulating the brain's visual cortex. Studies show that flashes in the range of about 5–30 times per second are most likely to provoke seizures (developer.mozilla.org). To protect users, the WCAG guidelines specifically require that video or animated content limit flashes.
What do the WCAG guidelines say about flashing content?
WCAG Success Criterion 2.3.1 requires that web content and videos do not flash more than three times per second. Success Criterion 2.3.1 (Three Flashes or Below Threshold, Level A) states that pages must not flash more than 3 times in any one-second period unless each flash is below defined brightness/size limits (w3.org, silktide.com). In other words, either limit yourself to 3 or fewer flashes per second, or ensure any faster flashes meet safety thresholds.
How do I make my video WCAG 2.2 AA compliant for flashing?
To achieve WCAG 2.2 AA compliance, your video must not flash more than three times per second or exceed luminance thresholds. If a sequence does flash rapidly, the flashes must remain below the General Flash and Red Flash Thresholds. You can use our analyzer to visualize these exact thresholds. If the analyzer detects a violation, you must edit your source video to slow down the frame rate of the flashing effect, lower the contrast of the bright flashes, or reduce the physical surface area of the flashing element on screen.