Development
No authHTTPSCORS
Development
W3C Validator
Validate HTML and check markup errors.
W3C Validator API is a free Development API that requires no API key, is served over HTTPS and has unconfirmed CORS support.
- Authentication
- None required
- HTTPS
- Yes
- CORS
- Unknown
- Category
- Development
Visit documentation ↗validator.w3.org
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W3C Validator API FAQ
Is the W3C Validator API free?
Yes. The W3C Validator API is listed in the Development category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Does the W3C Validator API require an API key?
No. The W3C Validator API requires no authentication, so you can start making requests without signing up.
Can I call the W3C Validator API from the browser?
CORS support for the W3C Validator API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Does the W3C Validator API support HTTPS?
Yes. The W3C Validator API is served over HTTPS, so it's safe to use in production.