HTTP 100 Continue vs 521 Web Server Is Down
HTTP 100 (Continue) is a 1xx Informational response, while 521 (Web Server Is Down) is a 5xx Server Error response. 100 indicates that the server has received the request headers and the client should proceed to send the request body. This lets the client know it can continue with the request or abort if the headers were rejected. In contrast, 521 means that cloudflare-specific. The origin server refused the connection.
Описание
The server has received the request headers and the client should proceed to send the request body. This lets the client know it can continue with the request or abort if the headers were rejected.
Когда вы это видите
When a client sends an Expect: 100-continue header, the server responds with 100 before the client sends the body.
Как исправить
This is an interim response — no fix needed. The client should continue sending the request body.
Описание
Cloudflare-specific. The origin server refused the connection.
Когда вы это видите
When Cloudflare can't establish a TCP connection to the origin server.
Как исправить
Check that the origin server is running and the firewall allows Cloudflare IPs.
Ключевые различия
100 is a 1xx Informational response, while 521 is a 5xx Server Error response.
HTTP 100: The server has received the request headers and the client should proceed to send the request body. This lets the client know it can continue with the request or abort if the headers were rejected.
HTTP 521: Cloudflare-specific. The origin server refused the connection.
You encounter 100 when when a client sends an Expect: 100-continue header, the server responds with 100 before the client sends the body.
You encounter 521 when when Cloudflare can't establish a TCP connection to the origin server.
Когда что использовать
For 100 (Continue): This is an interim response — no fix needed. The client should continue sending the request body. For 521 (Web Server Is Down): Check that the origin server is running and the firewall allows Cloudflare IPs.