HTTP 203 Non-Authoritative Information vs 520 Web Server Returned an Unknown Error
HTTP 203 (Non-Authoritative Information) is a 2xx Success response, while 520 (Web Server Returned an Unknown Error) is a 5xx Server Error response. 203 indicates that the response payload has been modified by a transforming proxy from the origin server's 200 response. In contrast, 520 means that cloudflare-specific. The origin server returned an unexpected response that Cloudflare could not process.
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
Cloudflare-specific. The origin server returned an unexpected response that Cloudflare could not process.
When You See It
When Cloudflare receives an empty, unknown, or malformed response from the origin.
How to Fix
Check origin server logs. Ensure responses include proper headers. Verify SSL configuration.
Key Differences
203 is a 2xx Success response, while 520 is a 5xx Server Error response.
HTTP 203: The response payload has been modified by a transforming proxy from the origin server's 200 response.
HTTP 520: Cloudflare-specific. The origin server returned an unexpected response that Cloudflare could not process.
You encounter 203 when when a proxy or CDN modifies the response body (e.g., adds headers, transforms content).
You encounter 520 when when Cloudflare receives an empty, unknown, or malformed response from the origin.
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 520 (Web Server Returned an Unknown Error): Check origin server logs. Ensure responses include proper headers. Verify SSL configuration.