100 Continue
1xx Informational
RFC 9110
Keep going — the server has seen your headers and isn't stopping you.
What 100 Continue means {#what}
The server received the request headers and is giving you the green light to send the body. It’s an interim response, meaning more is coming. You’ll usually only see this if your client explicitly asked for it via Expect: 100-continue.
When you’ll see a 100 {#when}
- Your HTTP client sent
Expect: 100-continuebefore uploading a large body - The server is confirming it accepts the request before you waste bandwidth sending a big payload