Continue

HTTP status code 100 (Continue) is a provisional response that indicates the initial part of a request has been received and has not yet been rejected by the server.

It is used to inform the client that the initial part of the request has been received and that the client should continue with the request or ignore it if it has already finished sending the request body.

The 100 (Continue) status code is often used in conjunction with the Expect header, where a client may send a request with the Expect: 100-continue header to inquire whether the server is willing to accept the request before the client sends the potentially large request body.

This mechanism is particularly useful for optimizing network usage when large requests are sent over the network. It allows the client to avoid sending large payloads if the server is going to reject the initial request based on header fields.

In essence, the 100 Continue status code acts as a preliminary handshake allowing more efficient data transmission and helping to prevent unnecessary resource usage by stopping oversized or inappropriate requests early in the communication process.