Continue
Informational (1xx)The 100 Continue status code indicates that the server has received the request headers and the client should proceed to send the request body. This interim response is used to optimize large request payloads — the client can check if the server will accept the request before transmitting the full body. It is part of the HTTP/1.1 expect-continue mechanism.
What is HTTP 100 Continue?
HTTP 100 Continue is a informational (1xx) status code. The 100 Continue status code indicates that the server has received the request headers and the client should proceed to send the request body. This interim response is used to optimize large request payloads — the client can check if the server will accept the request before transmitting the full body. It is part of the HTTP/1.1 expect-continue mechanism. Common causes include client sent an expect: 100-continue header and large file upload negotiation. This response indicates the server processed the request as expected.
Example Response
HTTP/1.1 100 Continue
Common Causes
- • Client sent an Expect: 100-continue header
- • Large file upload negotiation
- • Server acknowledging it is ready to receive the body
What to Know
- 1. This is not an error — it is a normal part of HTTP communication
- 2. If you see this unexpectedly, check if your HTTP client is sending the Expect header
- 3. Most HTTP libraries handle 100 Continue transparently
Frequently Asked Questions
When is the 100 Continue status used?
It is used when a client sends a large request body (like a file upload) and includes the 'Expect: 100-continue' header. The server responds with 100 to confirm it will accept the request before the client sends the full payload.
Do I need to handle 100 Continue in my code?
Usually not. Most HTTP clients and servers handle this transparently. You only need to worry about it if you are implementing a low-level HTTP parser or dealing with custom streaming protocols.
What happens if the server rejects after 100 Continue?
The server can still respond with a 4xx or 5xx error after sending 100 Continue. The 100 status only means the server is willing to receive the body, not that it will accept it.