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HTTP Status Code Simulator

Happy paths are easy; the 3 a.m. pager fires on the unhappy ones. Simulate the exact failure modes your retry logic, error boundaries, and alerting must survive: a clean 404 with a request ID for tracing, a 500 with an opaque incident reference, or a 429 that ships a Retry-After header your backoff code should respect.

compose payload

— validating —

exported mock url

▸ open mock ↗
simulated response headers

$ man status-codes

Everything above is encoded into the #data= fragment of the exported URL — deflated and base64url-packed by your browser. Fragments are never sent to any server, so this mock is shareable and private. Paste the URL anywhere: a teammate's browser decodes it identically.

grep -i related-searches

  • simulate 500 error response
  • test 404 api response online
  • http status code testing tool
  • mock 429 rate limit retry-after
  • api error response generator