WCAG 2.1 Contrast Ratio Calculator

x402

WCAG 2.1 Contrast Ratio Calculator is a paid API for AI agents from color.agentutil.net, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-10, last successful call 2026-04-29).

Calculates the WCAG 2.1 contrast ratio between a foreground and background color, and returns pass/fail results for AA and AAA accessibility standards at normal and large text sizes.

Price / call$0.001

Seller volume →—

Success100%

StatusUnknown

How this service works

Calculate WCAG 2.1 contrast ratio between two colors

Output

Returns a numeric contrast ratio (e.g. 21 for black-on-white), boolean pass/fail flags for WCAG 2.1 AA and AAA compliance at both normal and large text sizes, the normalized hex values of the input colors, a request ID, and a list of related agentutil services.

Example use cases

Example prompt

“What's the WCAG 2.1 contrast ratio between a white background (#FFFFFF) and dark navy foreground (#1A2E4A), and does it pass AA and AAA standards for both normal and large text?”

Technical details

Endpoint

POSThttps://color.agentutil.net/v1/contrast?utm_source=zero.xyz

When to prefer

Use this endpoint when you need to programmatically verify color accessibility compliance per WCAG 2.1 — especially when building or auditing UI components, design systems, or web pages and need pass/fail verdicts across all four WCAG contrast thresholds (AA/AAA × normal/large text) in a single call. Prefer this over manual calculation or generic color tools when you need structured, machine-readable results including the numeric ratio and boolean compliance flags.

Side effects

Invalid color format provided — returns error if hex, rgb(), hsl(), or CSS name cannot be parsed
Missing required field (background or foreground) — returns validation error
Unrecognized CSS color name — returns parsing error

Input

{
  "background": "#FFFFFF",
  "foreground": "#000000"
}

Schema · Request body

Field	Type	Description
background	string	Background color (hex, rgb(), hsl(), or CSS name)
foreground	string	Foreground color (hex, rgb(), hsl(), or CSS name)

Output

{
  "ratio": 21,
  "service": "https://color.agentutil.net",
  "aa_large": true,
  "aa_normal": true,
  "aaa_large": true,
  "aaa_normal": true,
  "background": "#ffffff",
  "foreground": "#000000",
  "request_id": "120f86e7-198b-41d3-98e1-6b2933b472ab",
  "related_services": [
    {
      "url": "https://verify.agentutil.net",
      "name": "verify",
      "description": "Fact verification against live data sources -- exchange rates, crypto, stocks, entities, geography"
    },
    {
      "url": "https://docs.agentutil.net",
      "name": "docs",
      "description": "Search pre-indexed platform documentation -- semantic vector search across 10+ platforms"
    },
    {
      "url": "https://think.agentutil.net",
      "name": "think",
      "description": "Intent security -- pre-flight safety checklists, instruction expansion, and post-action review for autonomous agents"
    },
    {
      "url": "https://convert.agentutil.net",
      "name": "convert",
      "description": "Unit conversion (80+ units), live currency rates, and encoding (base64, hex, URL)"
    },
    {
      "url": "https://weather.agentutil.net",
      "name": "weather",
      "description": "Current conditions and multi-day forecasts for any location worldwide via Open-Meteo"
    },
    {
      "url": "https://validate.agentutil.net",
      "name": "validate",
      "description": "Validate emails (RFC 5322), URLs, phone numbers (E.164), credit cards (Luhn), and JSON schemas"
    },
    {
      "url": "https://time.agentutil.net",
      "name": "time",
      "description": "Timezone conversion, current time in any timezone, date arithmetic, and epoch conversions"
    },
    {
      "url": "https://hash.agentutil.net",
      "name": "hash",
      "description": "Hash with MD5/SHA-256/SHA-512, encode/decode base64/hex/URL, generate UUIDs, identify hash algorithms"
    },
    {
      "url": "https://text.agentutil.net",
      "name": "text",
      "description": "Regex match/replace/extract, text diff, slugify, word count, and markdown/HTML/JSON transforms"
    },
    {
      "url": "https://math.agentutil.net",
      "name": "math",
      "description": "Safe expression evaluation, statistics (mean/median/stddev/percentiles), percentages, and rounding"
    },
    {
      "url": "https://geocode.agentutil.net",
      "name": "geocode",
      "description": "Forward geocoding (address to lat/lon), reverse geocoding (lat/lon to address), and haversine distance"
    },
    {
      "url": "https://dns.agentutil.net",
      "name": "dns",
      "description": "DNS record lookups (A/MX/TXT/NS), reverse DNS, WHOIS/RDAP domain data, and IP geolocation"
    },
    {
      "url": "https://undo.agentutil.net",
      "name": "undo",
      "description": "Reversibility intelligence -- check if actions can be undone, find safer alternatives, batch safety warnings"
    },
    {
      "url": "https://norm.agentutil.net",
      "name": "norm",
      "description": "Baseline reality checks -- statistical anomaly detection for values against published industry benchmarks"
    },
    {
      "url": "https://context.agentutil.net",
      "name": "context",
      "description": "Situational awareness -- timezone, holiday, business calendar, and platform status checks before taking action"
    },
    {
      "url": "https://random.agentutil.net",
      "name": "random",
      "description": "Secure random generation -- passwords, UUIDs (v4/v7), API tokens, numbers with dice notation, and random picks/shuffles"
    },
    {
      "url": "https://cron.agentutil.net",
      "name": "cron",
      "description": "Cron expression tools -- explain, parse natural language to cron, calculate next execution times, and validate expressions"
    },
    {
      "url": "https://useragent.agentutil.net",
      "name": "useragent",
      "description": "User agent parsing -- browser/OS/device detection, bot/crawler identification with 50+ patterns, and UA comparison"
    }
  ]
}

Schema · Response

Field	Type	Description
ratiorequired	number
servicerequired	string
aa_largerequired	boolean
aa_normalrequired	boolean
aaa_largerequired	boolean
aaa_normalrequired	boolean
backgroundrequired	string
foregroundrequired	string
request_idrequired	string
related_servicesrequired	array

Reviews

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How this service works

Calculate WCAG 2.1 contrast ratio between two colors

Output

Technical details

Endpoint

POSThttps://color.agentutil.net/v1/contrast?utm_source=zero.xyz

When to prefer

Side effects

Invalid color format provided — returns error if hex, rgb(), hsl(), or CSS name cannot be parsed
Missing required field (background or foreground) — returns validation error
Unrecognized CSS color name — returns parsing error

Input

{
  "background": "#FFFFFF",
  "foreground": "#000000"
}

Schema · Request body

Field	Type	Description
background	string	Background color (hex, rgb(), hsl(), or CSS name)
foreground	string	Foreground color (hex, rgb(), hsl(), or CSS name)

Output

{
  "ratio": 21,
  "service": "https://color.agentutil.net",
  "aa_large": true,
  "aa_normal": true,
  "aaa_large": true,
  "aaa_normal": true,
  "background": "#ffffff",
  "foreground": "#000000",
  "request_id": "120f86e7-198b-41d3-98e1-6b2933b472ab",
  "related_services": [
    {
      "url": "https://verify.agentutil.net",
      "name": "verify",
      "description": "Fact verification against live data sources -- exchange rates, crypto, stocks, entities, geography"
    },
    {
      "url": "https://docs.agentutil.net",
      "name": "docs",
      "description": "Search pre-indexed platform documentation -- semantic vector search across 10+ platforms"
    },
    {
      "url": "https://think.agentutil.net",
      "name": "think",
      "description": "Intent security -- pre-flight safety checklists, instruction expansion, and post-action review for autonomous agents"
    },
    {
      "url": "https://convert.agentutil.net",
      "name": "convert",
      "description": "Unit conversion (80+ units), live currency rates, and encoding (base64, hex, URL)"
    },
    {
      "url": "https://weather.agentutil.net",
      "name": "weather",
      "description": "Current conditions and multi-day forecasts for any location worldwide via Open-Meteo"
    },
    {
      "url": "https://validate.agentutil.net",
      "name": "validate",
      "description": "Validate emails (RFC 5322), URLs, phone numbers (E.164), credit cards (Luhn), and JSON schemas"
    },
    {
      "url": "https://time.agentutil.net",
      "name": "time",
      "description": "Timezone conversion, current time in any timezone, date arithmetic, and epoch conversions"
    },
    {
      "url": "https://hash.agentutil.net",
      "name": "hash",
      "description": "Hash with MD5/SHA-256/SHA-512, encode/decode base64/hex/URL, generate UUIDs, identify hash algorithms"
    },
    {
      "url": "https://text.agentutil.net",
      "name": "text",
      "description": "Regex match/replace/extract, text diff, slugify, word count, and markdown/HTML/JSON transforms"
    },
    {
      "url": "https://math.agentutil.net",
      "name": "math",
      "description": "Safe expression evaluation, statistics (mean/median/stddev/percentiles), percentages, and rounding"
    },
    {
      "url": "https://geocode.agentutil.net",
      "name": "geocode",
      "description": "Forward geocoding (address to lat/lon), reverse geocoding (lat/lon to address), and haversine distance"
    },
    {
      "url": "https://dns.agentutil.net",
      "name": "dns",
      "description": "DNS record lookups (A/MX/TXT/NS), reverse DNS, WHOIS/RDAP domain data, and IP geolocation"
    },
    {
      "url": "https://undo.agentutil.net",
      "name": "undo",
      "description": "Reversibility intelligence -- check if actions can be undone, find safer alternatives, batch safety warnings"
    },
    {
      "url": "https://norm.agentutil.net",
      "name": "norm",
      "description": "Baseline reality checks -- statistical anomaly detection for values against published industry benchmarks"
    },
    {
      "url": "https://context.agentutil.net",
      "name": "context",
      "description": "Situational awareness -- timezone, holiday, business calendar, and platform status checks before taking action"
    },
    {
      "url": "https://random.agentutil.net",
      "name": "random",
      "description": "Secure random generation -- passwords, UUIDs (v4/v7), API tokens, numbers with dice notation, and random picks/shuffles"
    },
    {
      "url": "https://cron.agentutil.net",
      "name": "cron",
      "description": "Cron expression tools -- explain, parse natural language to cron, calculate next execution times, and validate expressions"
    },
    {
      "url": "https://useragent.agentutil.net",
      "name": "useragent",
      "description": "User agent parsing -- browser/OS/device detection, bot/crawler identification with 50+ patterns, and UA comparison"
    }
  ]
}

Schema · Response

Field	Type	Description
ratiorequired	number
servicerequired	string
aa_largerequired	boolean
aa_normalrequired	boolean
aaa_largerequired	boolean
aaa_normalrequired	boolean
backgroundrequired	string
foregroundrequired	string
request_idrequired	string
related_servicesrequired	array