HTTP Status Codes
HTTP 100 Continue
Continue — the server has received the request headers and the client should proceed
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.
Visual summary
A quick reference view of how HTTP 100 works: A gatekeeper acknowledging the first piece of data and leaving the gate open for the remainder.
What 100 Means
The shortest useful reading of this status code.
Continue means the server has received the request headers and the client should proceed.
This status falls into the 1xx class, indicating a informational outcome for the request.
Quick read
Continue
the server has received the request headers and the client should proceed
Technical Context
How this status behaves without turning the page into a repair guide.
Standard usage
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.
Technical nuance
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.
Related HTTP Codes
Nearby HTTP status codes help clarify how 100 differs inside the same response family.
100
Continue
the server has received the request headers and the client should proceed
101
Switching Protocols
the server is switching to the protocol requested by the client
103
Early Hints
the server is sending preliminary response headers before the final response
417
Expectation Failed
the server cannot satisfy the request's Expect header requirements
Common Causes
Client sending a large request body with an Expect: 100-continue header
A common condition that triggers a 100 response when the web server evaluates the transaction.
Initial handshake in multi-part uploads
A common condition that triggers a 100 response when the web server evaluates the transaction.
Preliminary validation check before transmitting heavy payloads
A common condition that triggers a 100 response when the web server evaluates the transaction.
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 interpretation questions about HTTP 100.
Usually no. Browsers and HTTP libraries handle this status automatically as part of the request lifecycle.