203 Non-Authoritative Information (since HTTP/1.1)
This is an educational reference page about HTTP 203 Non-Authoritative Information. The page itself is served as 200 OK so it can be indexed as HTTP documentation.
The server is a transforming proxy (e.g. a Web accelerator) that received a 200 OK from its origin, but is returning a modified version of the origin's response.
Specification
Registered in the IANA HTTP Status Code Registry as Non-Authoritative Information. Defined in RFC 9110, Section 15.3.4.
Header and content rules
RFC 9110 adds no header or content rule specific to 203. See 203 in the response obligations table.