HTTP 411 Length Required vs 523 Origin Is Unreachable
HTTP 411 (Length Required) is a 4xx Client Error response, while 523 (Origin Is Unreachable) is a 5xx Server Error response. 411 indicates that the server refuses to accept the request without a Content-Length header. In contrast, 523 means that cloudflare-specific. Cloudflare could not reach the origin server (DNS resolution failed or no route).
Description
The server refuses to accept the request without a Content-Length header.
When You See It
When sending a request body without specifying Content-Length.
How to Fix
Include a Content-Length header in your request.
Description
Cloudflare-specific. Cloudflare could not reach the origin server (DNS resolution failed or no route).
When You See It
When Cloudflare's DNS for the origin fails to resolve.
How to Fix
Verify DNS records in Cloudflare dashboard. Check origin server's IP address.
Key Differences
411 is a 4xx Client Error response, while 523 is a 5xx Server Error response.
HTTP 411: The server refuses to accept the request without a Content-Length header.
HTTP 523: Cloudflare-specific. Cloudflare could not reach the origin server (DNS resolution failed or no route).
You encounter 411 when when sending a request body without specifying Content-Length.
You encounter 523 when when Cloudflare's DNS for the origin fails to resolve.
When to Use Which
For 411 (Length Required): Include a Content-Length header in your request. For 523 (Origin Is Unreachable): Verify DNS records in Cloudflare dashboard. Check origin server's IP address.