Check inline colour contrast API

Calculate a contrast ratio only when both colours are opaque values on the same element. A single colour is not compared with an assumed background.

The Check inline colour contrast operation is part of the Accessibility Intelligence API on BRAINIAC.software. Calculate a contrast ratio only when both colours are opaque values on the same element. A single colour is not compared with an assumed background. It is exposed as POST /api/v1/accessibility/color-contrast-check and priced at $0.04 USDC on Base. Payment uses the x402 exact scheme: an unpaid call returns HTTP 402 with payment requirements; after paying the exact USDC amount, retry the same request with a payment-signature header and Idempotency-Key. No account and no API key are required. Data sources for this product: HTML supplied in the request. One public HTML page fetched with the same public-page reader used by Web Intelligence. Limitations: Static HTML is not a WCAG conformance audit. JavaScript is not run, and browser or manual checks stay separate from confirmed issues. Contrast is calculated only when both colours are written on the same element. Stylesheet and inherited colours are not guessed. Outputs are compliance prechecks, drafts, or data lookups for human review. They are not official determinations, legal advice, identity confirmation, or certified filings. Related operations in this group include Audit HTML accessibility, Audit image alt text, Audit heading structure, Audit form accessibility. Open the group documentation for the full request schema, field notes, and response examples before integrating.

POST$0.04 USDC
/api/v1/accessibility/color-contrast-check

Example request

curl -i -X POST "https://www.brainiac.software/api/v1/accessibility/color-contrast-check" \
  -H 'content-type: application/json' \
  -H 'Idempotency-Key: <fresh-64-character-random-hex-key>' \
  --data-binary @- <<'JSON'
{
  "html": "<html lang=\"en\"><body><p style=\"color:#ffffff;background-color:#ffffff\">White</p><p style=\"color:#767676\">Grey</p></body></html>"
}
JSON

An unpaid probe returns HTTP 402 with x402 payment requirements. After paying the exact USDC amount on Base, retry the identical request with a payment-signature header.

FAQ

  • Do I need an API key? No. Pay the listed USDC amount with x402.
  • What network? Base (eip155:8453), USDC.
  • Is this an official determination? No. Results are for human review against the cited sources.

Related APIs

Accessibility Intelligence APIFull docsHow it works