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. (by Myndex)

SAPC-APCA Alternatives

Similar projects and alternatives to SAPC-APCA

NOTE: The number of mentions on this list indicates mentions on common posts plus user suggested alternatives. Hence, a higher number means a better SAPC-APCA alternative or higher similarity.

SAPC-APCA reviews and mentions

Posts with mentions or reviews of SAPC-APCA. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2022-05-20.
  • Change the colour of grey text back to black on website using poor contrast text
    3 projects | | 20 May 2022
    For a more future oriented version (as setting a font to black wont work with dark pages), check out the CSS Color Module Level 5 spec for color-contrast(), which will automatically choose a color that has a proper contrast ratio:

    One caveat is it's currently only supported in Safari technical preview.

    Another thing worth mentioning is the relative brightness algo used in the repo for the linked plugin is using the WCAG 2 formula for relative luminance. This works pretty well in light mode for non-colored backgrounds, but doesn't incorporate perceived luminosity differences of different hues very well. A better algorithm to use here is the Advanced Perceptual Contrast Algorithm (APCA), which is the one used in the WCAG 3 working spec. It more accurately accounts for hue:

  • Please Stop Using Grey Text
    10 projects | | 18 May 2022
    Note the licensing note in the repository[1] of the APCA™ index the author’s company[2] promotes:

    > The files currently in this repository are presently considered pre-release, and as such do not have a permanent license attached. In this repositiory, all files present are under a time-barred beta license, and intended for use with web-based content only, and not for any other use without written permission.

    The non-pre-release stuff[3] offered to W3C is better but still seems to be intended to end up non-FOSS:

    > Files in this repository are licensed to the W3/AGWG under their cooperative agreement for use with WCAG accessibility guidelines for web-based content only, and not for any other use.

    (The question being, of course, how much of this is copyrightable at all.)




  • WCAG 3 and updated contrast checkers?
    4 projects | /r/UXDesign | 15 Dec 2021
    Fifth: If you want to use APCA or BPCA, then welcome to the open beta test, and feel free to say hi in the beta thread at the GitHub repo:
    4 projects | /r/UXDesign | 15 Dec 2021
    On an additional note, apart from the WCAG 3.0 Working Draft, this piece from Andrew Somers, who is working on APCA for WCAG 3, and this twitter thread might be of use.
    4 projects | /r/UXDesign | 15 Dec 2021
    Second: There are a number of contrast checkers that use APCA technology. The canonical "official" one is but I want to mention it is an open public beta, and is not backwards compatible with WCAG_2 (this is in part because WCAG_2 is not perceptually accurate and thus the areas where WCAG_2 incorrectly fails pairs that APCA will pass is at issue).
    4 projects | /r/UXDesign | 15 Dec 2021
  • I made a tool to check the contrast between two colours using the new contrast algorithm being drafted for WCAG 3 — also includes fun rgb/hsl/lch sliders and buttons to adjust either colour to a desired contrast!
    2 projects | /r/web_design | 27 Oct 2021
    Andrew Somers W3 AGWG Invited Expert Color Science Researcher Myndex Perception Research Inventor APCA/co-author WCAG3
    2 projects | /r/web_design | 27 Oct 2021
    Thank you! I'm not sure this would make sense as an npm package — it's just a web page. The source code is on github in case it inspires anybody, and the contrast calculation is based on the algorithm that Myndex has also shared:
  • A note from our sponsor - Onboard AI | 2 Dec 2023
    Onboard AI learns any GitHub repo in minutes and lets you chat with it to locate functionality, understand different parts, and generate new code. Use it for free at Learn more →


Basic SAPC-APCA repo stats
about 1 month ago
Learn any GitHub repo in 59 seconds
Onboard AI learns any GitHub repo in minutes and lets you chat with it to locate functionality, understand different parts, and generate new code. Use it for free at