generated: '2026-09-07'
method: searched
source: https://jigsaw.w3.org/css-validator/manual.html#requestformat
api: W3C CSS Validation Service
limit_count: 1
summary: >-
  W3C publishes exactly one limit for the public CSS Validation Service, and it is a stated
  courtesy obligation on the caller rather than an enforced quota: a script validating a batch
  of documents must sleep at least one second between requests. No quota, no burst allowance
  and no per-key ceiling is published, because there are no keys.
limits:
  - scope: per-caller
    window: 1s
    limit: 1
    burst: null
    unit: requests
    enforcement: documented-courtesy
    applies_to: all endpoints of https://jigsaw.w3.org/css-validator/validator
    quote: >-
      "If you wish to call the validator programmatically for a batch of documents, please
      make sure that your script will sleep for at least 1 second between requests. The CSS
      Validation service is a free, public service for all, your respect is appreciated."
    source: https://jigsaw.w3.org/css-validator/manual.html#requestformat
response_headers:
  observed: []
  note: >-
    Probed 2026-09-07 against the live service: the response carried no X-RateLimit-*,
    RateLimit-* or Retry-After header. There is no runtime rate-limit signal an agent can
    read — the one-second interval must be honored by the client from the documentation.
exhaustion:
  status_code: null
  note: >-
    W3C does not publish what the service returns when the courtesy interval is ignored, and
    no attempt was made to provoke it. Recording an unknown rather than guessing a 429.
remedy: >-
  Callers with volume needs are directed to run their own instance instead of raising a limit
  on the public one — the validator is distributed as a jar and a war for exactly that reason
  (https://jigsaw.w3.org/css-validator/DOWNLOAD.html).