APCA is the Advanced Perceptual Contrast Algorithm, developed by Myndex Research and proposed for WCAG 3.0. Instead of a ratio it outputs an Lc value, and it scores dark-on-light and light-on-dark pairs differently.

What Lc value do I need?

For normal body text, Lc 60+ is recommended (roughly equivalent to WCAG AA). For large headings, Lc 45+ is sufficient. Lc 90+ provides excellent readability for all users.

Is APCA the same as WCAG 2.x contrast?

APCA and WCAG 2.x are different. They use different formulas and scales. A colour pair that passes WCAG 2.x may not score well on APCA, and vice versa. APCA is not yet an official standard.

Why does swapping text and background change the Lc score?

APCA treats the two polarities differently. #767676 text on white scores Lc 71.6, and white text on #767676 scores Lc 77.0, while the WCAG 2.x ratio is 4.54:1 both ways.

APCA contrast checker

APCA (Advanced Perceptual Contrast Algorithm) is a contrast method proposed for WCAG 3.0 and not yet part of a W3C standard. It reports an Lc score instead of a ratio and scores dark text on a light background differently from light text on a dark background. This page shows the Lc score with general guidance for body text and headings. It does not apply APCA's font size and weight tables.

Foreground (text)

Background

Aa Large text sampleNormal body text sample, the quick brown fox jumps over the lazy dog.

Lc 106.0

● Lc 90+: excellent readability for all text sizes

APCA-W3 0.0.98G · not yet an official standard

MODE

PRESETS

Runs entirely in your browser

How it works

WCAG contrast is computed using relative luminance: each sRGB channel is linearised (gamma-corrected), then combined as L = 0.2126R + 0.7152G + 0.0722B. The ratio is (L1 + 0.05) / (L2 + 0.05) where L1 is the lighter colour. APCA uses the separate APCA-W3 0.0.98G algorithm which accounts for polarity and produces an Lc value. All computation runs entirely in your browser.

Processing runs in your browser

All contrast calculations happen in your browser tab. Our servers are not involved at any point.

Related operations

To swap a HEX value into RGB or HSL while testing, try the colour converter. For generating an accessible swatch set from a brand colour, use the colour palette generator. To create lighter or darker variants that still pass contrast, see tints and shades.

Frequently asked questions

What is APCA?: APCA is the Advanced Perceptual Contrast Algorithm, developed by Myndex Research and proposed for WCAG 3.0. Instead of a ratio it outputs an Lc value, and it scores dark-on-light and light-on-dark pairs differently.
What Lc value do I need?: For normal body text, Lc 60+ is recommended (roughly equivalent to WCAG AA). For large headings, Lc 45+ is sufficient. Lc 90+ provides excellent readability for all users.
Is APCA the same as WCAG 2.x contrast?: APCA and WCAG 2.x are different. They use different formulas and scales. A colour pair that passes WCAG 2.x may not score well on APCA, and vice versa. APCA is not yet an official standard.
Why does swapping text and background change the Lc score?: APCA treats the two polarities differently. #767676 text on white scores Lc 71.6, and white text on #767676 scores Lc 77.0, while the WCAG 2.x ratio is 4.54:1 both ways.

Last reviewed September 30, 2026

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