HTTP 426 Upgrade Required vs 523 Origin Is Unreachable
HTTP 426 (Upgrade Required) is a 4xx Client Error response, while 523 (Origin Is Unreachable) is a 5xx Server Error response. 426 indicates that the server refuses to perform the request using the current protocol but might after the client upgrades to a different protocol. 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 perform the request using the current protocol but might after the client upgrades to a different protocol.
When You See It
When a server requires HTTPS or a newer protocol version.
How to Fix
Switch to the protocol specified in the Upgrade response header.
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
426 is a 4xx Client Error response, while 523 is a 5xx Server Error response.
HTTP 426: The server refuses to perform the request using the current protocol but might after the client upgrades to a different protocol.
HTTP 523: Cloudflare-specific. Cloudflare could not reach the origin server (DNS resolution failed or no route).
You encounter 426 when when a server requires HTTPS or a newer protocol version.
You encounter 523 when when Cloudflare's DNS for the origin fails to resolve.
When to Use Which
For 426 (Upgrade Required): Switch to the protocol specified in the Upgrade response header. For 523 (Origin Is Unreachable): Verify DNS records in Cloudflare dashboard. Check origin server's IP address.