generated: '2026-09-07'
method: searched
source: https://jigsaw.w3.org/css-validator/manual.html#requestformat
docs: https://jigsaw.w3.org/css-validator/api.html
api: W3C CSS Validation Service
summary: >-
  The W3C CSS Validation Service is an open, anonymous, unauthenticated web service. It
  issues no credentials, has no sign-up, no API key, no OAuth and no token of any kind. The
  User Manual states plainly that it is "a free, public service for all" and asks callers to
  self-throttle instead of authenticating. An agent needs no secret to call it; what it needs
  is the courtesy rate limit recorded in rate-limits/css-rate-limits.yml.
model: anonymous
schemes: []
credentials_required: false
sign_up_required: false
transport:
  https: true
  http_methods: [GET, POST]
  note: >-
    POST is used for the file-upload form; the programmatic interface documented in the User
    Manual is a plain HTTP GET against the base URI with query parameters.
identity_signals:
  - signal: none
    note: >-
      No account, tenant or caller identity exists. Requests are distinguished only by the
      document being validated, which is echoed back as the uri/TestSubject field.
self_hosting:
  note: >-
    The same servlet can be run privately (java -jar css-validator.jar, or deployed as a war
    under Tomcat or Jigsaw), in which case the operator supplies whatever authentication their
    container enforces. See cli/css-cli.yml.
  source: https://jigsaw.w3.org/css-validator/DOWNLOAD.html
verification:
  probed: '2026-09-07'
  url: https://jigsaw.w3.org/css-validator/validator?text=a%7Bcolor%3Ared%7D&output=json&profile=css3
  http_status: 200
  note: >-
    Called with no credentials of any kind and returned a complete validation result, which
    confirms the anonymous model rather than inferring it from prose.