APCA (Lc) vs WCAG 2.1 Ratio
WCAG 2.1 ratios remain the binding legal benchmark today, while APCA catches dark-mode readability failures that simple luminance division misses.
APCA (Lc)
Advanced Perceptual Contrast Algorithm modeling polarity-aware (dark-on-light vs light-on-dark) and font-weight-aware human readability.
Visit APCA (Lc)WCAG 2.1 Ratio
Current legal and compliance standard measuring relative luminance ratios (`4.5:1` AA normal text, `3:1` large text, `7:1` AAA).
Visit WCAG 2.1 RatioFeature Comparison
| Feature | APCA (Lc) | WCAG 2.1 Ratio | OKLCH Color Scale, WCAG & APCA Contrast Studio |
|---|---|---|---|
| Polarity sensitivity | Distinguishes dark vs light bg | Symmetric for swapped pairs | Side-by-side Lc & ratio |
| Regulatory status | WCAG 3 working draft guidance | Current EN 301 549 / ADA standard | Pass/fail AA, AAA & Lc |
| Dark-mode accuracy | Prevents halation & muddy grays | Can over-approve dim dark pairs | Live dark/light preview |
Verdict
Enforce WCAG 2.1 AA (`4.5:1`) for formal compliance, and check APCA (`Lc >= 60–75` for body copy) simultaneously to ensure crisp dark-mode typography.
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Try it freeFrequently Asked Questions
What is the difference between APCA (Lc) and WCAG 2.1 Ratio?
WCAG 2.1 ratios remain the binding legal benchmark today, while APCA catches dark-mode readability failures that simple luminance division misses. On the points that matter most: Polarity sensitivity — APCA (Lc): Distinguishes dark vs light bg; WCAG 2.1 Ratio: Symmetric for swapped pairs. Regulatory status — APCA (Lc): WCAG 3 working draft guidance; WCAG 2.1 Ratio: Current EN 301 549 / ADA standard. Dark-mode accuracy — APCA (Lc): Prevents halation & muddy grays; WCAG 2.1 Ratio: Can over-approve dim dark pairs.
Is APCA (Lc) better than WCAG 2.1 Ratio?
Enforce WCAG 2.1 AA (`4.5:1`) for formal compliance, and check APCA (`Lc >= 60–75` for body copy) simultaneously to ensure crisp dark-mode typography. If you mainly need the core feature without a subscription or signup, OKLCH Color Scale, WCAG & APCA Contrast Studio is a free alternative to both.
Is there a free alternative to both APCA (Lc) and WCAG 2.1 Ratio?
Yes — our OKLCH Color Scale, WCAG & APCA Contrast Studio is completely free with no account required.