HTTP 100 Continue is an interim response indicating the server has received the request headers and the client should proceed to send the request body. This status is crucial for optimizing large payload uploads — the client sends an Expect: 100-continue header, and the server either replies 100 to accept the body or 417 to reject it early, saving bandwidth. Without this mechanism, clients would blindly transmit potentially megabytes of data only to receive a 401 or 413 after the full upload completes.
Response includes the status code, standard headers (including Content-Type), and a small diagnostic JSON body describing the request and returned status.
Simulator URL (copy in the app after load — not a normal link):
https://httpstatus.com/api/status/100
Example request:
curl -i "https://httpstatus.com/api/status/100"