WCAG Text Contrast Checker API

Accessibility

Check colour contrast ratios to ensure accessibility compliance with WCAG guidelines (Level AA and AAA).

Authentication

All API requests require a valid API key passed in the Authorization header as a Bearer token.

Rate Limit

100 requests per minute

Endpoints

2 endpoints available

Overview

The WCAG Text Contrast Checker API validates colour contrast ratios against Web Content Accessibility Guidelines (WCAG). Check if your text and background colour combinations meet Level AA or AAA compliance standards.

WCAG Standards

Level AA (Normal Text) - Minimum contrast ratio of 4.5:1
Level AA (Large Text) - Minimum contrast ratio of 3:1 (18pt+ or 14pt bold)
Level AAA (Normal Text) - Minimum contrast ratio of 7:1
Level AAA (Large Text) - Minimum contrast ratio of 4.5:1

Check Types

WCAG Compliance - Check against AA and AAA standards with font size consideration
Custom Ratio - Check against a custom minimum contrast ratio
Batch Check - Check multiple colour pairs at once

Use Cases

Web design accessibility audits
Design system colour validation
Automated accessibility testing pipelines
UI/UX design reviews
Brand colour accessibility verification

Endpoints

POST

/v1/tools/wcag-text-checker

Check colour contrast for WCAG compliance

Request Body

Content-Type: application/json

Parameter	Type	Required	Description
textColour	string	Required	Text colour in hex format (e.g., "#000000")
backgroundColour	string	Required	Background colour in hex format (e.g., "#FFFFFF")
fontSize	number	Optional	Font size in pixels (used to determine large text threshold)Default: `14`
checkType	string Enum: wcag, custom	Optional	Type of check to performDefault: `wcag`
customRatio	number	Optional	Custom minimum contrast ratio (1-21, only used when checkType is "custom")Default: `4.5`

Response Example

{
  "success": true,
  "contrastRatio": "12.63",
  "wcagAA": true,
  "wcagAAA": true,
  "textColour": "#1a1a1a",
  "backgroundColour": "#ffffff",
  "fontSize": 16,
  "isLargeText": false
}

Error Codes

400

Invalid colour format or missing required parameters

401

Missing or invalid API key

429

Rate limit exceeded

500

Internal server error

POST

/v1/tools/wcag-text-checker/batch

Check multiple colour pairs at once

Request Body

Content-Type: application/json

Parameter	Type	Required	Description
pairs	array	Required	Array of colour pairs to check, each with textColour, backgroundColour, and optional fontSize

Response Example

{
  "success": true,
  "results": [
    {
      "textColour": "#000000",
      "backgroundColour": "#ffffff",
      "contrastRatio": "21.00",
      "wcagAA": true,
      "wcagAAA": true
    },
    {
      "textColour": "#666666",
      "backgroundColour": "#ffffff",
      "contrastRatio": "5.74",
      "wcagAA": true,
      "wcagAAA": false
    }
  ]
}

Error Codes

400

Invalid colour format or empty pairs array

401

Missing or invalid API key

429

Rate limit exceeded

500

Internal server error

Code Examples

# Single colour pair check
curl -X POST https://api.opentools.ca/v1/tools/wcag-text-checker \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"textColour": "#333333", "backgroundColour": "#f5f5f5", "fontSize": 16}'

# Batch check multiple pairs
curl -X POST https://api.opentools.ca/v1/tools/wcag-text-checker/batch \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"pairs": [{"textColour": "#000000", "backgroundColour": "#ffffff"}, {"textColour": "#0066cc", "backgroundColour": "#ffffff"}]}'

Ready to get started?

Create an API key to start using the WCAG Text Contrast Checker API.