Contrast (Minimum)
Body text must have a luminance contrast ratio of at least 4.5:1 against its background; large text (≥18pt or ≥14pt bold) needs at least 3:1.
What it requires
Color contrast is the most-violated WCAG criterion on the web — affecting 81% of homepage scans according to WebAIM 2024. Pale-grey body text on white backgrounds, brand colors that look fine to designers but fail the 4.5:1 luminance threshold, and disabled-state buttons that are too dim are the most common failures.
The luminance formula is defined in WCAG and not equivalent to color difference or hue rotation. Tools like WebAIM Contrast Checker and Colour Contrast Analyser compute it correctly.
Common Shopify failure
Default theme colors set to `#999` body text on `#fff`, which yields a 2.85:1 ratio (failing). Brand orange buttons on white that fall to 3.4:1 (passing for large but failing if used on small captions).
How to fix it
AccessComply's ColorContrastAgent finds the closest brand-aligned color that meets the threshold — typically darkening lightness by 5-15% while preserving hue — and writes the change as a CSS custom property override at the top of the theme's base.css.
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 1.4.3 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 1.4.3 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 safe automatic 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 1.4.3