WCAG3 Still Has No Contrast Algorithm — APCA Was Never It

The WCAG 3.0 Editor's Draft dated 8 April 2026 defines its "contrast ratio test" as "meeting a sufficient level of contrast between two colors using the relationship of hue, saturation, and lightness values" — and carries an editor's note stating plainly: "The contrast algorithm used in WCAG 3 is yet to be determined."

That sentence settles a question that has produced years of bad advice in the design community. Teams, products, and organizations have promoted APCA (Accessible Perceptual Contrast Algorithm) as the WCAG3 contrast algorithm, and in many cases recommended dismissing the contrast requirements in WCAG 2.x altogether. Neither claim matches the standards track record.

APCA held only an "Exploratory" maturity label in WCAG3 drafts, and the working group removed it in early 2023. Under the WCAG 3 development process, exploratory content that does not gain working group support to proceed to the next stage within six months is removed automatically. Michael Cooper of the W3C wrote on 30 January 2023, in issue #663 on the Visual contrast thread: "We still hope the promising contrast work will continue to mature for potential later inclusion." The July 2023 WCAG3 working draft shipped without APCA, and the W3C's accompanying update explained the removal of exploratory items at that time.

Even the creator of APCA acknowledged the problem with the versions that had appeared in the draft, calling them all "early versions that were very obsolete" — emphasis theirs — in a response to Cooper's comment.

The practical consequences reach further than tool preferences. Claims that APCA is the WCAG3 algorithm create legal exposure for anyone who acts on them, particularly in jurisdictions whereWCAG 2.x conformance anchors legal or contractual accessibility obligations. The problematic advice circulated widely enough that the author of the underlying analysis began filing issues with tool makers to remove APCA — including a May 2024 Chromium issue — and publicly rebutted a January 2025 post promoting the dismiss-WCAG2 approach on Mastodon and Bluesky, where the APCA creator also weighed in.

What design teams should do now

Using APCA remains an option, whatever version you choose. The risk-management question is what happens when your color palette fails WCAG 2.x contrast requirements. Two approaches limit exposure:

1. Choose colors that also conform to WCAG 2.x contrast requirements — the 4.5:1 ratio for body text under Success Criterion 1.4.3 Contrast (Minimum) remains the compliance baseline regulators and courts recognize.
2. If you deliberately pick colors that fail WCAG 2.x, document the decision and prepare a response for a drive-by lawsuit from a bad actor running an automated checker to surface a contrast violation — assuming your attorney signs off.

The timeline makes this patience justified. The W3C's own WCAG3 timeline puts completion years away, perhaps 2030 at the soonest, and any contrast algorithm WCAG3 adopts will not be final until at least then. Designers who want to adopt whatever gets proposed before 2030 face the same two options above.

The author notes he is not speaking on behalf of the W3C or the Accessibility Guidelines Working Group, is not a member, and has no insider knowledge of the group's deliberations.

Whether APCA returns to WCAG3 in some future version remains unknown — but until the working group writes an actual algorithm into the draft, WCAG 2.x contrast ratios remain the only contrast requirements with normative weight.