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SESK: Stuff Everyone Should Know · sesk.info/tech-http-5xx-server-error

An HTTP status code starting with 5, like 500, means what?

The server failed to handle a request that looked valid.

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  1. The page was moved
  2. Your request had bad syntax
  3. The server failed on a valid-looking request ✔

Why: The first digit gives the class: 2xx success, 3xx redirect or more action needed, 4xx client error like 404, and 5xx server error. A 500 means the problem is on the server's side, not yours.

Huh, didn't know that: 201 Created means a request worked and made a new resource, a common reply to a successful POST.

The dad joke
I asked the server for a joke and got a 500. Turns out that was the joke.
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References

Answer: The server failed on a valid-looking request. The first digit gives the class: 2xx success, 3xx redirect or more action needed, 4xx client error like 404, and 5xx server error. A 500 means the problem is on the server's side, not yours.

  1. RFC 9110: HTTP Semantics, Section 15 www.rfc-editor.org/rfc/rfc9110
    The server failed to fulfill an apparently valid request
    Checked 2026-10-11.

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