203 Non-Authoritative Information

What is HTTP 203?

This status code means the request was successful, but the response payload has been modified by a transforming proxy from what the origin server originally sent. The data is valid but may not match exactly what the origin server intended. It allows the client to know that the information might have been altered by a middleware or caching layer. This code is rarely used in practice, as most proxies do not signal their modifications.

Defined in RFC 9110

Common Causes

• A proxy or CDN modified response headers or body content before forwarding
• Content transformation by a middleware layer such as compression or format conversion
• A local cache returning data that may have been altered from the original

How to Fix

• If accuracy is critical, request the resource directly from the origin server
• Check proxy and CDN configurations to understand what transformations are applied
• Compare the response with a direct request to identify any differences