This interim response indicates that everything so far is OK and that the client should continue the request, or ignore the response if the request is already finished.
Definition:
In HTTP status codes, 100 Continue is an informational response that indicates that the initial part of a client’s request has been received by the server, and the client can continue with the request or ignore the response if the request is already finished.
It is used in situations where a client sends a request that includes a large payload (e.g., a file upload), but before sending the full payload, the client wants to ensure that the server is prepared to handle it. The server responds with 100 Continue to indicate that the client should proceed with the request.
Purpose:
- Informational: The 100 status code is part of the 1xx class of status codes, which are used to indicate that the request was received and understood, but that further action is needed to complete it.
- Pre-request Confirmation: It allows the client to check whether it should continue with the rest of its request, particularly in cases where the request includes a body (such as file uploads or form submissions). This prevents the client from sending a large payload if the server has already rejected the request due to some preliminary checks (like authentication).
Typical Usage:
- Client-Server Communication: When a client makes an HTTP request to the server using a method like
POSTorPUT, and that request might involve a large payload, the client can send a smaller header portion first. The server then responds with 100 Continue if everything is in order, signaling that the client should continue sending the rest of the data.
Example of Usage:
- Client Request (Initial):