What HTTP 100 means
A client uploading a large body can first send only the headers with Expect: 100-continue. The server answers 100 if it will accept the body, or an error like 401 or 413 if not, so the client doesn’t waste bandwidth uploading data that would be rejected. curl sends Expect: 100-continue automatically for large POST bodies.
Using 100 correctly
-
If an upload stalls for a second before starting, the server may be ignoring
Expect. SendExpect:(empty) with curl to disable it.
Retrying
Not applicable: this isn’t an error.
Example response
HTTP/1.1 100 ContinueRelated status codes
- 417 Expectation Failed : The server can’t meet the requirement in the Expect header.
- 413 Content Too Large : The request body is larger than the server allows.
- 101 Switching Protocols : The server agrees to switch to the protocol the client asked for, such as WebSocket.
Other 1xx status codes
101 Switching Protocols · 103 Early Hints
See the full list of HTTP status codes.
Sources
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Frequently asked questions
What does HTTP 100 Continue mean?
HTTP 100 Continue tells the client to go ahead and send the request body. A client uploading a large body can first send only the headers with Expect: 100-continue. The server answers 100 if it will accept the body, or an error like 401 or 413 if not, so the client doesn’t waste bandwidth uploading data that would be rejected. curl sends Expect: 100-continue automatically for large POST bodies.