Definition
Contrast ratios rely on relative luminance of pairs of colours. Good luminance contrast matters for readability and accessibility.
Best Practices
- Target a contrast ratio above 4.5 for body text.
- Recompute contrast for your palette in dark mode.
- Use a contrast checker before finalising brand colours.
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Related Glossary Terms
Above the Fold in Email
Above the fold in email refers to the content visible to a recipient before they scroll, a critical area for first impressions and primary calls to action.
Accessible CTA (Email)
An accessible CTA is a button or link coded with sufficient colour contrast, visible focus states, descriptive screen-reader text, and a minimum touch target of 44×44 pixels.
Adaptive Design
Adaptive design in email uses predefined layouts that adjust to specific device or client widths, rather than fluidly resizing to every possible screen.
AI-Generated Content in Email
AI-generated content in email is copy, images, code or subject lines produced by artificial intelligence tools to speed up campaign production and testing.
Alt Text
Alt text is the written alternative to an image in an email, displayed when images are blocked, slow to load, or consumed by screen readers.
Autoplay Video in Email
Autoplay video in email refers to the limited ability to play video content automatically when an email is opened, using specific client-supported techniques.
Frequently Asked Questions
It is the basis of WCAG contrast ratio calculations.
Above 4.5 for normal text; above 3 for large text and UI.
Auto-inverted backgrounds change perceived contrast dramatically.