This is the APCA project repo on GitHub.
Documentation linked below.


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APCA Documentation Repo


APCA™ is the Accessible Perceptual Contrast Algorithm, a new way to predict contrast for text and non-text content on self-illuminated displays. This repository is for the documentation, for issue tracking, and for the discussion forum. The code, apps, variants, and supporting libraries, are in separate repos.

Simple Overview & QuickStart

These are intended for end users, and those interested in a plain language overview without a lot of the math & theory.

Additional documentation



For comments or questions see the SAPC-APCA forum here, please post all comments, questions, or discussions regarding theory, math, code, third-party tools, etc., here and not in the satellite repositories, so they can be tracked and resolved. Discussion here may eventually become part of the FAQ and guidelines.



Sciency Stuff!

Maths! Vision Science! Photons on Parade!

Poster: a picture of crash test dummies crashing out of a car, and text that says don't be a dummy! Stop using low contrast text. At the bottom it says APCA the world is reading       Smokey the bear saying  ONLY YOU CAN STOP LOW CONTRAST      Uncle Sam saying I want you to use high contrast text

Social Media

Local Repo Documentation

The SAPC APCA Documentation Repository

You are here 🎯 this index page is served at the github APCA documentation repo.

The APCA-W3 GitHub Repo

Over there is the APCA W3 version, and it’s the same as the published npm package “apca-w3”.

The Bridge-PCA GitHub Repo

The BridgePCA is backwards compatible with WCAG 2, and it’s the same as the published npm package “bridge-pca”.

The ColorParsley GitHub Repo

ColorParsley is a micro library for auto parsing color strings of all kinds, also on npm.

The SeeStars GitHub Repo

SeeStars is a micro library for creating CIE Lstar $(L*)$, also on npm.

The ColorParsley GitHub Repo

DeltaPhiStar is an ultra simple general purpose contrast equation.

APCA Contrast Calculator

The canonical demo tool at Myndex

Bridge PCA Contrast Calculator

Try out the Bridge PCA tool at Myndex

Myndex CVD Simulator

Color insensitive vision simulation (aka colorblind). Includes deuteranopia, protanopia, tritanopia, and blue cone monochromacy/achromatopsia.

Inclusive Reading Technologies, Inc.

IRT is a California nonprofit, dedicated to developing tecnologies to improve visual accessibility for all, and home to the APCA Readability Criterion.

Basic APCA Math in LaTeX

The APCA base color-pair formula, in math notation. 0.0.98G-4g

APCA The Revolution Will Be Readable

Apkah Happy ReadCow

link to Delta Phi Star repo

IRT logo link to IRT

link to COLOR a twitter community

link to IRT