100 Continue

HTTP 100 Continue is an interim response used to inform the client 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 it if the request is already finished.

Sent when a client includes an Expect: 100-continue header before transmitting a large request body, allowing the server to reject the request early.

• Client sent Expect: 100-continue header
• Large file upload using a two-phase handshake
• HTTP/1.1 client politely checking before sending body

• This is not an error — no action required
• Ensure your client library correctly handles 100 Continue responses
• If the server never sends 100 Continue, increase the client timeout for the expect handshake

HTTP/1.1 100 Continue