metric @community/metric-contrast-ratio

Contrast Ratio

The WCAG-specified luminance contrast ratio between a foreground color and a background color. Used to assess whether text and UI components meet accessibility thresholds.

Skill: @community
Domain: accessibility
Version: 1.0.0
Quality: 4.0
Edges: 3 out · 8 in
Tokens: 58/338/619

$ prime install @community/metric-contrast-ratio

Projection

3 levels · agent picks one per query

Always in _index.xml · the agent never has to ask for this.

wcag-contrast-ratio [metric] v1.0.0

The WCAG-specified luminance contrast ratio between a foreground color and a background color. Used to assess whether text and UI components meet accessibility thresholds.

Loaded when retrieval picks the atom as adjacent / supporting.

wcag-contrast-ratio [metric] v1.0.0

The WCAG-specified luminance contrast ratio between a foreground color and a background color. Used to assess whether text and UI components meet accessibility thresholds.

Unit

ratio (unitless)

Formula

(L1 + 0.05) / (L2 + 0.05)

Variables

L1: relative luminance of the lighter color (0.0–1.0)
L2: relative luminance of the darker color (0.0–1.0)

Sub Formula

Label: relative-luminance
Description: Per WCAG 2.2 definition of relative luminance from IEC 61966-2-1:1999

Body:

      For each sRGB channel c in [R, G, B]:
        c_linear = c_srgb / 255
        if c_linear <= 0.04045:
          c_lin = c_linear / 12.92
        else:
          c_lin = ((c_linear + 0.055) / 1.055) ^ 2.4
      L = 0.2126 * R_lin + 0.7152 * G_lin + 0.0722 * B_lin

Thresholds

- Level: AA-normal-text
- Min: 4.5
- Criterion: @w3c/fact-wcag-contrast-aa
- Level: AA-large-text
- Min: 3
- Criterion: @w3c/fact-wcag-contrast-aa
- Level: AAA-normal-text
- Min: 7
- Level: AA-ui-component
- Min: 3
- Criterion: @w3c/fact-wcag-contrast-aa
- Level: focus-ring
- Min: 3
- Criterion: @w3c/fact-wcag-focus-contrast

Range

Min: 1
Max: 21

Loaded when retrieval picks the atom as a focal / direct hit.

wcag-contrast-ratio [metric] v1.0.0

The WCAG-specified luminance contrast ratio between a foreground color and a background color. Used to assess whether text and UI components meet accessibility thresholds.

Unit

ratio (unitless)

Formula

(L1 + 0.05) / (L2 + 0.05)

Variables

L1: relative luminance of the lighter color (0.0–1.0)
L2: relative luminance of the darker color (0.0–1.0)

Sub Formula

Label: relative-luminance
Description: Per WCAG 2.2 definition of relative luminance from IEC 61966-2-1:1999

Body:

      For each sRGB channel c in [R, G, B]:
        c_linear = c_srgb / 255
        if c_linear <= 0.04045:
          c_lin = c_linear / 12.92
        else:
          c_lin = ((c_linear + 0.055) / 1.055) ^ 2.4
      L = 0.2126 * R_lin + 0.7152 * G_lin + 0.0722 * B_lin

Thresholds

- Level: AA-normal-text
- Min: 4.5
- Criterion: @w3c/fact-wcag-contrast-aa
- Level: AA-large-text
- Min: 3
- Criterion: @w3c/fact-wcag-contrast-aa
- Level: AAA-normal-text
- Min: 7
- Level: AA-ui-component
- Min: 3
- Criterion: @w3c/fact-wcag-contrast-aa
- Level: focus-ring
- Min: 3
- Criterion: @w3c/fact-wcag-focus-contrast

Range

Min: 1
Max: 21

Unit

ratio (unitless)

Formula

(L1 + 0.05) / (L2 + 0.05)

Variables

L1: relative luminance of the lighter color (0.0–1.0)
L2: relative luminance of the darker color (0.0–1.0)

Sub Formula

Label: relative-luminance
Description: Per WCAG 2.2 definition of relative luminance from IEC 61966-2-1:1999

Body:

      For each sRGB channel c in [R, G, B]:
        c_linear = c_srgb / 255
        if c_linear <= 0.04045:
          c_lin = c_linear / 12.92
        else:
          c_lin = ((c_linear + 0.055) / 1.055) ^ 2.4
      L = 0.2126 * R_lin + 0.7152 * G_lin + 0.0722 * B_lin

Thresholds

- Level: AA-normal-text
- Min: 4.5
- Criterion: @w3c/fact-wcag-contrast-aa
- Level: AA-large-text
- Min: 3
- Criterion: @w3c/fact-wcag-contrast-aa
- Level: AAA-normal-text
- Min: 7
- Level: AA-ui-component
- Min: 3
- Criterion: @w3c/fact-wcag-contrast-aa
- Level: focus-ring
- Min: 3
- Criterion: @w3c/fact-wcag-focus-contrast

Range

Min: 1
Max: 21

Source

where the compiled artifact came from

prime-system/examples/frontend-design/primes/compiled/@community/metric-contrast-ratio/atom.yaml

Compiled at 2026-05-07