HTTP 101 Switching Protocols vs 521 Web Server Is Down
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 521 (Web Server Is Down) is a 5xx Server Error response. 101 indicates that the server understands the Upgrade header field request and indicates which protocol it is switching to. In contrast, 521 means that cloudflare-specific. The origin server refused the connection.
Beschreibung
The server understands the Upgrade header field request and indicates which protocol it is switching to.
Wann Sie es sehen
When upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
Wie man es behebt
This is normal behavior during protocol upgrades. Ensure your client supports the target protocol.
Beschreibung
Cloudflare-specific. The origin server refused the connection.
Wann Sie es sehen
When Cloudflare can't establish a TCP connection to the origin server.
Wie man es behebt
Check that the origin server is running and the firewall allows Cloudflare IPs.
Wesentliche Unterschiede
101 is a 1xx Informational response, while 521 is a 5xx Server Error response.
HTTP 101: The server understands the Upgrade header field request and indicates which protocol it is switching to.
HTTP 521: Cloudflare-specific. The origin server refused the connection.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 521 when when Cloudflare can't establish a TCP connection to the origin server.
Wann welchen verwenden
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 521 (Web Server Is Down): Check that the origin server is running and the firewall allows Cloudflare IPs.