Short answer
Not as a replacement, not yet. APCA (the Accessible Perceptual Contrast Algorithm) is a proposed method, still in beta validation, developed as a candidate for WCAG 3; the WCAG 3 Working Draft has not adopted it or any other contrast method. WCAG 2.2's ratio remains the normative test for conformance and legal purposes. APCA can be a useful second opinion, especially for dark mode and for white text on mid-tones, as long as the WCAG 2.2 result is what you report.
WCAG 2.2 is a W3C Recommendation and is also published as ISO/IEC 40500:2025; its contrast ratio is what conformance claims, procurement rules and most accessibility laws refer to. WCAG 3 is a separate, differently structured project. The Working Draft dated 10 September 2026 keeps its contrast guideline at an early stage: its text uses a placeholder where a contrast measure would go and states that the contrast algorithm for WCAG 3 is yet to be determined. APCA's own repository describes it as being in beta validation and developed as an assessment method for WCAG 3. Neither the draft nor APCA changes what WCAG 2.2 requires today.
The WCAG 2 ratio compares the relative luminance of two colours with a simple formula that is symmetric: swapping text and background gives the same number. APCA outputs a lightness-contrast value, Lc, on a scale running roughly from −108 to +106, and its sign depends on polarity — dark text on a light background and light text on a dark background produce different values, because perceived contrast is not symmetric. Its guidance ties target Lc values to font size and weight rather than to a single threshold: its readme presents Lc 75 as a target for fluent body text, Lc 90 as a preferred level, and progressively lower values (60, 45, 30, 15) for larger or less critical content. These are the proposal's own recommendations, not W3C requirements.
The table shows one of the best-known disagreements, using only the WCAG 2 formula. On saturated mid-tone backgrounds — orange, bright blue, red, green — WCAG 2 often rates black text as higher-contrast than white, and in several cases white text fails 4.5:1 while black passes. Many designers and readers find white text on such colours at least as readable, which is part of the motivation for perceptual models. WCAG 2 is also criticised for rating some dark-on-dark pairs too generously, which matters most in dark themes. Colourwise's reading is that these are real limitations of a 2008-era formula but that it is conservative in most everyday cases; the disagreements concentrate in mid-tones and very dark colours.
Meet WCAG 2.2 first; that is the standard you can be held to. Where it produces an odd result — white text failing on a mid-tone brand colour that looks perfectly readable — you have two compliant options: darken the background slightly until white text passes, or use black text. An APCA check can tell you which of those gives the better perceptual result, and it is informative for dark-mode palettes, font-weight choices and very small text. Do not describe a design as 'APCA compliant' in a conformance statement, since there is no such standard, and treat any APCA figures as advisory. Revisit this when WCAG 3 moves beyond Working Draft and names a method.
| Background | White text | Black text | WCAG 2 prefers |
|---|---|---|---|
| #FF6600 | 2.93:1 | 7.15:1 ✓ | Black |
| #1E90FF | 3.23:1 | 6.48:1 ✓ | Black |
| #E53935 | 4.22:1 | 4.96:1 ✓ | Black |
| #43A047 | 3.30:1 | 6.35:1 ✓ | Black |
| #8E24AA | 7.03:1 ✓ | 2.98:1 | White |
| #00897B | 4.31:1 | 4.86:1 ✓ | Black |
Why: APCA was treated as a standard.
Fix: Report WCAG 2.2 results for conformance; use APCA only as an advisory check.
Why: The WCAG 2 formula favours dark text on mid-tones.
Fix: Darken the orange until white passes 4.5:1, or use black text.
Why: Uncertainty about which method will be adopted.
Fix: Fix to WCAG 2.2 now; a darker, clearer design will not be penalised later.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactStrong evidence
The WCAG 3.0 Working Draft dated 10 September 2026 has not specified a contrast method; its contrast text uses a placeholder and states that the contrast algorithm for WCAG 3 is yet to be determined.
Caveat: Working Drafts change; this describes the version reviewed.
Source: W3C Accessibility Guidelines (WCAG) 3.0 — Working Draft
FactModerate evidence
APCA is described by its author as in beta validation and developed as an assessment method for WCAG 3; it produces a polarity-dependent lightness-contrast value (Lc) from about −108 to +106 and ties recommended Lc levels to font size and weight.
Caveat: APCA is a proposal, not a W3C standard, and is not part of any WCAG Recommendation.
Source: APCA — Accessible Perceptual Contrast Algorithm (apca-w3 repository)
Colourwise analysisStrong evidence
On several saturated mid-tone backgrounds the WCAG 2 formula rates black text higher than white, and white text falls below 4.5:1.
Based on: Computed by Colourwise with the WCAG 2.2 contrast formula; see the table.
Source: Web Content Accessibility Guidelines (WCAG) 2.2; Understanding Success Criterion 1.4.3: Contrast (Minimum) (WCAG 2.2)
Colourwise interpretationLimited evidence
WCAG 2's symmetric luminance ratio misjudges perceived contrast in some mid-tone and dark-on-dark combinations, but remains a conservative and adequate test for most everyday text colours.
Based on: Colourwise's reading of the known criticisms that motivated APCA and the WCAG 3 contrast work, together with the computed examples on this page.
Caveat: Perceptual studies comparing the two methods are ongoing and not settled.
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.