Accessible Perceptual Contrast Algorithm (APCA)

Accessible Perceptual Contrast Algorithm (APCA) es el nuevo método para calcular el contraste entre colores que va a sustituir al método actual que se emplea en WCAG.

En Why APCA as a New Contrast Method? explican:

Readability is a critically important aspect of web content, affecting 99% of internet users. For years, the WCAG 2.x contrast guidelines provided some guidance toward readability but are being replaced for the future WCAG 3.0. Here is an overview of the need for this change and discussion of the candidate replacement, the Accessible Perceptual Contrast Algorithm (APCA).

WCAG 2.x contrast and 1.4.3 and the related understandings and guidelines were born in an era before smart phones and iPads, when displays were mostly CRT type and websites used core web fonts. But that was a decade and a half ago. Today the contrast guidelines are in need of a complete overhaul due to the massive changes in computer display technology, web content, CSS functionality, and advances in vision science since 2005/2008, when WCAG 2.x was first introduced. For deeper background, see the author’s thread circa April 2019 in WCAG issue 695.

There are a number of reasons that WCAG 2.x contrast is faulty, one of which is the binary pass/fail nature of the SC for a property that does not apply in a binary way across perception nor impairments. Humans are not binary computers, and it is important to understand the non-linear aspects of perception, and to set guidelines that correctly model perception as opposed to “brute forcing” arbitrary values that ultimately do more harm than good.

Y APCA CONTRAST CALCULATOR es una herramienta online que permite calcular la diferencia de contraste según el nuevo algoritmo.