HTTP 100 Continue

What does HTTP 100 mean?

The server has received the request headers and the client may send the body. A client that sends Expect: 100-continue (curl does this for large uploads) waits for this interim response before uploading, so it does not waste bandwidth if the server would reject the request anyway.

1xx Informational: The request was received and processing continues. Browsers handle these automatically; you rarely see them in DevTools.

100 and SEO

No SEO impact — crawlers never see interim responses as final status codes.

Example response

HTTP/1.1 100 Continue

Related status codes

• 101 Switching Protocols — The server agrees to switch to the protocol named in the client’s Upgrade header.
• 103 Early Hints — An interim response that lets the server send Link headers before the final response is ready.
• 417 Expectation Failed — The server cannot meet the requirement in the request’s Expect header.

Check which status code a URL returns with the HTTP header checker.