HTTP 203 Non-Authoritative Information means the request was successful but the response payload has been modified by a transforming proxy between the origin server and the client. The returned content may differ from the origin's 200 OK response.
Status
203 Non-Authoritative InformationExample
GET /news/latest HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0
Accept: text/htmlHTTP/1.1 203 Non-Authoritative Information
Content-Type: text/html; charset=utf-8
Via: 1.1 cdn.example.com
Content-Length: 452
<!doctype html>
<html lang="en">
<head>
<title>Latest News - Example</title>
</head>
<body>
<h1>Latest News</h1>
<p>Showing a cached version of this page served through our CDN.</p>
</body>
</html>How to Troubleshoot
Compare with origin response
Request the resource directly from the origin to see the unmodified version.
curl -v --resolve example.com:443:ORIGIN_IP https://example.com/
Check Via header
The Via header identifies which proxy modified the response.
Bypass the proxy if needed
If the proxy modification is causing issues, access the origin directly or configure the proxy to pass through unmodified.
Common Causes
Proxy modified the response
highA transparent proxy or CDN transformed the response body (e.g., image compression, content rewriting) before returning it.
Content adaptation service
mediumA mobile content adaptation proxy modified the response for a different device format.
Related Status Codes
References
| Specification | Section |
|---|---|
| HTTP Semantics | RFC 9110 §15.3.4 |
Frequently Asked Questions
This reference was compiled from official RFCs, protocol specifications, and hands-on troubleshooting experience. AI tools were used primarily for formatting and organizing the content on the page.