What does HTTP status code 100 mean?
The 100 Continue status code is an informational response indicating that the initial part of the request has been received and has not yet been rejected by the server. The client should continue with the request or ignore this response if the request has already been finished.
When to use it in APIs
Typically used in large file uploads (like media or bulk datasets) using the Expect: 100-continue header. The client sends headers first to check if the server will accept the request (based on authorization, content size, etc.) before uploading the heavy body payload.
How it compares to other codes
- 103 Early Hints: Used to send headers (like preloading assets) before the final response, whereas 100 is strictly a gatekeeper for body uploads.
