Continue — the server has received the request headers and the client should proceed
What 100 Means
The 100 error on the HTTP Status-Codes indicates continue — the server has received the request headers and the client should proceed. This typically occurs due to client sending a large request body with an expect: 100-continue header.
A 100 Continue status is an interim response indicating that everything so far is OK and that the client should continue with the request or ignore it if it is already finished. It is primarily used to prevent clients from sending large payloads if the server is going to reject the request based on headers alone.
Technical Background
The 100 Continue status is an interim response that informs the client that the initial part of the request has been received and has not yet been rejected by the server.
This is primarily used with the 'Expect: 100-continue' header, allowing a client to verify if the server will accept a large request body (like a file upload) before actually sending it, thus saving bandwidth and processing time.
Common Causes
- Client sending a large request body with an Expect: 100-continue header
- Initial handshake in multi-part uploads
- Preliminary validation check before transmitting heavy payloads
Typical Scenarios
- An API client waits for a 100 Continue before uploading a multi-gigabyte file
- A browser checks if the server will accept a POST request before transmitting the body
What to Know
Observation of a 100 status in logs indicates a successful handshake for large payload transfers. Modern HTTP clients handle this transition automatically without requiring manual intervention.
Frequently Asked Questions
Common questions about HTTP 100 error
Usually no. Browsers and HTTP libraries handle this status automatically as part of the request lifecycle.