203 Non-Authoritative Information

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

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 the 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.

The 203 response is similar to the 214 Transformation Applied value of the deprecated Warning header, which may be applicable to responses with any status code.

Status

http
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.

http
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
HTTP/1.1 203 Non-Authoritative Information
Date: Wed, 26 Jun 2024 12:00:00 GMT
Server: 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"
}

Specifications

Specification
HTTP Semantics
# status.203

See also