WCAG defines two levels of contrast compliance, AA and AAA, and the naming does nobody any favours — it sounds like AAA is simply “more accessible” and therefore what you should always aim for. The reality is more useful than that. Here’s the plain-English version.
The numbers, side by side
| AA (the standard) | AAA (the stretch) | |
|---|---|---|
| Normal text | 4.5:1 | 7:1 |
| Large text | 3:1 | 4.5:1 |
“Large” means at least 18pt (~24px) regular, or 14pt (~18.66px) if bold.
You can flip the contrast checker between these two levels with the Strict mode (AAA) toggle and watch which sizes pass or fail for your colours.
What AA is
AA is the practical standard for the web. It’s the level referenced by essentially every law and policy that touches digital accessibility — the ADA case law in the US, EN 301 549 and the European Accessibility Act in Europe, the public-sector rules in the UK. When someone says a site “meets WCAG,” they almost always mean AA.
If you do nothing else, target AA. It’s achievable across an entire site without contorting your design, and it’s the bar you’re realistically going to be measured against.
What AAA is
AAA is a genuinely high standard — and WCAG itself says so. The guidelines explicitly note that AAA conformance isn’t achievable for all content, and they do not recommend it as a general policy for entire sites. It’s a level you reach for where you can, not a blanket requirement.
That said, AAA contrast (7:1 for body text) is a lovely thing to hit for your main reading content. Text at 7:1 is comfortable for people with moderate visual impairments, not just the mild ones AA covers. If your body copy can clear it without wrecking your palette, do it.
So which should you aim for?
A sensible policy for most projects:
- Meet AA everywhere. Non-negotiable. Every piece of text, every button outline, every icon.
- Aim for AAA on body text where it’s easy. Long-form reading content benefits most, and dark-grey-on-white gets you there without drama.
- Don’t torture your brand to hit AAA on everything. WCAG doesn’t ask you to, and forcing it often means throwing away colours that were fine at AA.
A subtlety worth knowing
Higher contrast is safe up to a point, but a small number of readers — some people with dyslexia or light sensitivity — find pure black on pure white harsh. That’s why many well-designed sites use a very dark grey (say #1a1a1a) on an off-white rather than #000 on #FFF. You can sit comfortably above 7:1 while being a little kinder to those readers. You can’t fail a check for having too much contrast, but you can make text feel sharp.
The bottom line
- AA (4.5:1 / 3:1) is the standard you’re held to. Meet it everywhere.
- AAA (7:1 / 4.5:1) is a stretch goal, best applied to body text where it’s easy.
- AAA is not a universal requirement — WCAG itself doesn’t ask for it site-wide.
Check where your colours land against both levels in the contrast checker, and use the strict-mode toggle to see the AAA picture.