APCA (Accessible Perceptual Contrast Algorithm) is a new method for predicting contrast for use in emerging web standards (WCAG 3) for determining readability contrast. APCA is derived form the SAPC (S-LUV Advanced Predictive Color) which is an accessibility-oriented color appearance model designed for self-illuminated displays.

The APCA version, to be licensed for use with guidelines: W3/AGWG.

Figma plugin for displaying the contrast level and font size recommendations according to the APCA method

𝜟𝜱✴︎ or Delta Phi Star is a variant method of determining lightness contrast, and a sibling of APCA and SACAM. It is a simplified version using easily invertible standardized maths, however it lacks some useful properties such as polarity sensitivity. In fact, it is intended for applications where a "general" simplifed perceptual contrast is des…

A simplified version of the APCA math to bridge from WCAG_2 contrast math to the future, while being 100% backwards compatible with WCAG_2 contrast. By "backwards compatible" we mean if bridge-pca passes it, it will automatically pass WCAG_2 contrast.

Axe rules to check against APCA bronze and silver+ conformance levels.

A TypeScript package to calculate WCAG 2.0/3.0 and APCA color contrasts

A catalog of Myndex Research content, including APCA articles & documentation, related code repositories, and resources.

The missing introduction to APCA

An accessible color scheme backed by scientific research.

Send it the background color, returns black or white whichever is maximum Lc value

A color contrast checker that supports WCAG 2, APCA & Focus Colors

A tool to check for color contrast using APCA

Sass implementation of the Accessible Perceptual Contrast Algorithm (APCA) for the WCAG 3.0 specification.

See Stars is a Myndex MicroColor Library. This has standard functions for the standard (piecewise) IEC conversion of sRGB to Y, and the CIE standard Y to L* (Lstar) and back again. The math & constants here reference those of CSS 4 for compatibility.

The corrected introduction to APCA, a rebuttal and discussion of xi's repo from which this is forked.

Deterministic, explainable design-quality measurement for any live URL — CSS health, Oklab/APCA color science, Shannon entropy, AI-UI detection, and DESIGN.md compliance. Runs locally, no API key.

Design audit for Claude Code. Scores UI/UX across 12 dimensions grounded in 24 named UX laws with primary-source citations. WCAG + APCA + OKLCH. Zero deps.

ARC • APCA Readability Criterion — a set of web-standard guidelines for text and non-text for use with the APCA contrast algorithm. Latest published version at this link:

RGAA v4.1.2 accessibility compliance analyzer for NextJS projects