APCA is the Advanced Perceptual Contrast Algorithm developed by Myndex Research for use in WCAG 3.0. Unlike the WCAG 2.x ratio, APCA outputs an Lc value that better matches human perception.

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.

APCA contrast checker

APCA (Advanced Perceptual Contrast Algorithm) is the contrast model being developed for WCAG 3.0. It is more perceptually accurate than the WCAG 2.x ratio method, accounting for polarity (light-on-dark vs dark-on-light) and font weight.

Foreground (text)

Background

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

Lc 98.4

● 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 for use in WCAG 3.0. Unlike the WCAG 2.x ratio, APCA outputs an Lc value that better matches human perception.
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.

APCA contrast checker

How it works

Processing runs in your browser

Related operations

Frequently asked questions

Related tools