Three Flashes or Below Threshold
Web pages must not contain anything that flashes more than three times in any one-second period, unless the flashing is below specific brightness thresholds.
What it requires
WCAG 2.0 SC 2.3.1 protects users with photosensitive epilepsy and migraine sensitivity. Flashing content that exceeds three flashes per second in a sufficiently bright/contrasting region can trigger seizures.
The threshold is technical: the flashing must stay below 25% screen area or below specific luminance/red-flash thresholds. In practice, ecommerce sites should avoid flashing content entirely except for very small UI accents.
Common Shopify failure
Promotional carousel that auto-cycles every 0.3 seconds with high-contrast color shifts. Flash-sale banner with rapid red/yellow color flashing.
How to fix it
AccessComply detects animation rules with sub-300ms iteration cycles on background-color or filter properties and flags them for merchant review. Auto-fix slows the iteration to a safe 1.5s minimum.
Merchant QA checklist
- Scan the storefront page where this pattern appears: product pages, collection pages, cart drawer, customer-account pages, and any landing page built with theme sections.
- Confirm the issue is fixed in the rendered browser output, not only in the Liquid file. Shopify section settings, app blocks, and third-party scripts can reintroduce the same 2.3.1 failure after a theme edit.
- Re-test the affected component with keyboard navigation and a screen-reader accessibility tree before publishing the theme, especially when the fix changes markup or ARIA attributes.
How AccessComply handles it
AccessComply treats WCAG 2.3.1 as a rendered-storefront issue first. The scanner checks the live DOM and computed styles, maps the finding back to the Shopify theme file that produced it, then classifies the fix as a guided partial fix. When automation is safe, the app writes the smallest theme-code change needed and keeps the original theme backup available. When merchant judgment is required, the issue is surfaced for manual review instead of pretending the page is fixed.
Primary source: W3C — WCAG 2.0 Understanding 2.3.1