203 Non-Authoritative Information

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About

The HTTP 203 Non-Authoritative Information successful response status code indicates that the request was successful, but a transforming proxy has modified the header or enclosed content from the origin server’s 200 OK response 1.

Purpose of the 203 status code

The purpose of this status code is to allow transforming proxies to notify clients when changes have been applied to successful responses , since this may impact decisions regarding content later. Transformations to messages can mean modifications of headers to indicate that a resource is from a mirror or a backup , but may also mean modifying content in a way that are presumed to be desirable to the client . These modifications might include malware filtering , format transcoding , privacy filtering, or other hints to the client about future requests .

Status

203 Non-Authoritative Information

Examples

Receiving a filtered message response

In this example, a user sends a GET request for content with ID 123 to example.com:

GET /comments/123 HTTP/1.1
Host: example.com

A proxy has altered the message based on malware filtering rules for known unsafe attachments. The response content has been modified, replacing the attachment_url value to a link with information about the filtering in place:

HTTP/1.1 203 Non-Authoritative Information
Date: Sat, 10 May 2025 05:48:00 GMT
Serer: Apache/2.4.1 (Unix)
Content-Type: application/json
Content-Length: 123

{
  "comment": "Check out my bio!",
  "attachment_url": "https://example.com/attachment-unavailable-faq"
}

Anki

References

  1. MDN. “203 Non-Authoritative Information”. Available at: https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/203 . (Accessed: [2025-05-09 Fri 05:51]). ↩︎

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