HTTP 203 Non-Authoritative Information vs 428 Precondition Required
HTTP 203 (Non-Authoritative Information) is a 2xx Success response, while 428 (Precondition Required) is a 4xx Client Error response. 203 indicates that the response payload has been modified by a transforming proxy from the origin server's 200 response. In contrast, 428 means that the server requires the request to be conditional (e.g., include If-Match header) to prevent lost updates.
Description
The response payload has been modified by a transforming proxy from the origin server's 200 response.
When You See It
When a proxy or CDN modifies the response body (e.g., adds headers, transforms content).
How to Fix
Check if a proxy is modifying the response. Access the origin directly if you need the original content.
Description
The server requires the request to be conditional (e.g., include If-Match header) to prevent lost updates.
When You See It
When an API requires optimistic concurrency control via ETags.
How to Fix
Fetch the resource first to get its ETag, then include If-Match in your update request.
Key Differences
203 is a 2xx Success response, while 428 is a 4xx Client Error response.
HTTP 203: The response payload has been modified by a transforming proxy from the origin server's 200 response.
HTTP 428: The server requires the request to be conditional (e.g., include If-Match header) to prevent lost updates.
You encounter 203 when when a proxy or CDN modifies the response body (e.g., adds headers, transforms content).
You encounter 428 when when an API requires optimistic concurrency control via ETags.
When to Use Which
For 203 (Non-Authoritative Information): Check if a proxy is modifying the response. Access the origin directly if you need the original content. For 428 (Precondition Required): Fetch the resource first to get its ETag, then include If-Match in your update request.