---
name: contrast-advanced
type: heuristic
version: 2.0.0
tags: [contrast, apca, wcag-3, accessibility]
---

# Advanced Contrast Auditing

Use WCAG 2.2 contrast ratios as the release baseline. APCA is an optional design-quality signal for typography exploration; it is not a WCAG 2.2 conformance method and must not replace the normative ratios.

## Normative WCAG 2.2 floor

- Normal text: at least 4.5:1.
- Large text: at least 3:1.
- Essential component boundaries, states, focus indicators, and graphical objects: at least 3:1 against adjacent colors under Success Criterion 1.4.11.
- Incidental, inactive, and purely decorative graphics are exempt; do not use the exemption for information or affordances.

Compute sRGB relative luminance after linearizing each channel, then use `(L1 + 0.05) / (L2 + 0.05)`, where `L1` is the lighter luminance. Test the rendered state, including hover, focus, disabled, selected, light, and dark variants.

Primary standard: [WCAG 2.2, Contrast (Minimum)](https://www.w3.org/TR/WCAG22/#contrast-minimum) and [Non-text Contrast](https://www.w3.org/TR/WCAG22/#non-text-contrast).

## Audited reference pairs

The ratios below are calculated with the WCAG sRGB formula and rounded to two decimals:

| Foreground | Background | Ratio | WCAG interpretation |
|---|---|---:|---|
| #666666 | #FFFFFF | 5.74:1 | Passes normal-text AA |
| #0066CC | #FFFFFF | 5.57:1 | Passes normal-text AA |
| #FF6600 | #0033AA | 3.48:1 | Passes large text/non-text only; fails normal text |
| #888888 | #FFFFFF | 3.54:1 | Passes large text/non-text only; fails normal text |

Recalculate any changed pair. Never copy a rounded result to a different color, opacity, blend mode, or background.

## Using APCA responsibly

APCA produces a signed lightness-contrast value and uses font size and weight in its guidance. Its algorithm and guidance can change while WCAG 3 develops. Therefore:

1. Record the calculator implementation/version and access date.
2. Record polarity, font family, size, and weight.
3. Treat APCA as an additional signal for legibility, not a waiver for a WCAG 2.2 failure.
4. Do not translate an APCA result into a claimed WCAG ratio, or vice versa; the models do not have a stable one-to-one conversion.

When APCA and WCAG point in different directions, first adjust the colors or typography to satisfy both. If that is impossible, WCAG 2.2 remains the conformance gate and the APCA result remains documented design evidence.

See [accessibility.md](./accessibility.md) for the complete WCAG 2.2 baseline.