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Accessibility Contrast Audit

Design & Media · by AIDiveForge · Apr 20, 2026 · Beginner

Calculate text contrast for supplied colors and document the rendered context.

Get contrast ratios, applicable thresholds and candidate color adjustments.

Download skill ZIP See the worked example

Free · 2 KB · SKILL.md, instructions and example files. Provide foreground/background colors and text size/weight; rendered pages require browser access.

A worked example

A small example to try before using your own data.

Input

{
  "foreground": "#777777",
  "background": "#FFFFFF",
  "text": "16px regular"
}

Expected result

{
  "contrast_ratio_rounded": 4.48,
  "normal_text_AA": "fail",
  "candidate_foreground": "#767676",
  "candidate_ratio_rounded": 4.54
}

What to check: Compare using the unrounded ratio; 4.48 must not be rounded up to a 4.5 pass.

Limits: This checks text contrast, not complete WCAG conformance. Gradients, images, transparency and non-text controls require their own context checks.

Worked example included. Model-specific performance and vendor compatibility have not been benchmarked.

Installation options and other formats

Install this skill

An agent skill starts with SKILL.md. The ZIP also includes its examples and any helper scripts. Drop the file into your tool of choice — or pick a different format if you use Cursor, Windsurf, Copilot, or something else.

Download SKILL.md 
python3 - <<'ADF_SKILL_INSTALL'
import hashlib, io, os, stat, tempfile, urllib.request, zipfile
from pathlib import Path, PurePosixPath
folder = "accessibility-contrast-audit"
root = Path(os.environ.get('ADF_SKILL_ROOT', str(Path.home() / '.claude' / 'skills'))).expanduser()
destination = root / folder
if destination.exists() or destination.is_symlink():
    raise SystemExit('An installation already exists. Back it up and merge the ZIP deliberately.')
root.mkdir(parents=True, exist_ok=True)
request = urllib.request.Request("https://aidiveforge.com/skill/accessibility-contrast-audit.zip", headers={'User-Agent': 'AIDiveForge-Resource-Installer/1.0 (+https://aidiveforge.com/skills/)'})
with urllib.request.urlopen(request, timeout=30) as response:
    data = response.read(8 * 1024 * 1024 + 1)
if len(data) > 8 * 1024 * 1024 or hashlib.sha256(data).hexdigest() != "502bdc58c836365f5de4b9bd76f3485480e0faa9cf07480a685e9091432cb615":
    raise SystemExit('The download did not match this reviewed bundle. No files were installed.')
with zipfile.ZipFile(io.BytesIO(data)) as archive, tempfile.TemporaryDirectory(prefix='.adf-skill-', dir=root) as temporary:
    members = archive.infolist()
    if len(members) > 100 or sum(m.file_size for m in members) > 16 * 1024 * 1024:
        raise SystemExit('Unexpected archive size')
    for member in members:
        name = PurePosixPath(member.filename)
        if name.is_absolute() or '..' in name.parts or not name.parts or name.parts[0] != folder or '\\' in member.filename or stat.S_ISLNK(member.external_attr >> 16):
            raise SystemExit('Unsafe archive entry; nothing was installed')
        target = Path(temporary).joinpath(*name.parts)
        if member.is_dir():
            target.mkdir(parents=True, exist_ok=True)
        else:
            target.parent.mkdir(parents=True, exist_ok=True)
            with target.open('xb') as stream:
                stream.write(archive.read(member))
    staged = Path(temporary) / folder
    if not (staged / 'SKILL.md').is_file() or destination.exists() or destination.is_symlink():
        raise SystemExit('The skill could not be installed without replacing existing data')
    os.rename(staged, destination)
print('Installed the complete skill folder:', destination)
ADF_SKILL_INSTALL

Claude Code: ~/.claude/skills/accessibility-contrast-audit/SKILL.md. Codex: ~/.codex/skills/accessibility-contrast-audit/SKILL.md. Keep the complete ZIP folder when helper scripts are included.

🧠 Why it works

Compare using the unrounded ratio; 4.48 must not be rounded up to a 4.5 pass.

⚙️ How it works

  1. Resolve actual foreground and background colors, including opacity, layered backgrounds and interaction states.
  1. Convert sRGB channels to linear light and calculate relative luminance and (L1+0.05)/(L2+0.05).
  1. Compare with the applicable WCAG text threshold: 4.5:1 for normal text, 3:1 for qualifying large text.
  1. Propose a small color adjustment and recalculate it against the same background.
  1. Inspect the rendered result and report context that a flat color calculation cannot establish.

Description

Get contrast ratios, applicable thresholds and candidate color adjustments.

Provide foreground/background colors and text size/weight; rendered pages require browser access.

Limits: This checks text contrast, not complete WCAG conformance. Gradients, images, transparency and non-text controls require their own context checks.

Recommended Use

Tools and workflow packs this skill pairs well with. Forge picks are auto-generated from category + capability signals; Community picks are added by people who've used the pairing.

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