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.

• Updated Apr 17, 2025
• CSS

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

• Updated Sep 14, 2023
• JavaScript

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

• Updated Jul 22, 2025
• TypeScript

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...

• Updated Apr 29, 2024
• HTML

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

• Updated Jun 30, 2025
• TypeScript

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

• Updated Oct 15, 2025
• TypeScript

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.

• Updated Jun 18, 2023
• JavaScript

The missing introduction to APCA

• Updated Aug 26, 2025
• JavaScript

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

• Updated Apr 30, 2025
• CSS

An accessible color scheme backed by scientific research.

• Updated May 6, 2025
• Lua

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

• Updated Sep 1, 2023
• JavaScript

A tool to check for color contrast using APCA

• Updated Sep 13, 2023
• TypeScript

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

• Updated Oct 22, 2025
• SCSS

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.

• Updated Aug 10, 2022
• JavaScript

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:

• Updated Mar 25, 2023
• HTML

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

• Updated Apr 26, 2025
• JavaScript

A repo collecting the more substantial comments Myndex made regarding typography, CSS, color, contrast, and vision.

• Updated Apr 11, 2025

Canonical rebuttals to sponsored rumors regarding APCA, APC-RC, BridgePCA, etc.

• Updated Apr 30, 2025

This is the APCA Web Tool for technology demonstration at apcacontrast.com

• Updated Apr 18, 2025
• CSS

For a number of years now, work has been proceeding in order to bring perfection to the cryptically conceived concept of contrast that would not only supply inverse reactive spatial quanta for use in unilateral phase detractors, but would also be capable of automatically syncing cardinal grameters. Such an algorithm is the Turbo Contrastulator.

• Updated Oct 3, 2024