100 Continue

What it means

A client that sends Expect: 100-continue waits for this interim response before uploading a large body, which avoids sending data the server would reject anyway.

Common causes

• The client sent an Expect: 100-continue header.
• A large upload is being negotiated before the body is sent.

How to fix it

1. No action is needed; the final status follows after the body is sent.
2. If uploads stall, check that proxies forward 100 Continue correctly.

Example response

HTTP/1.1 100 Continue

Worked example

A client sends Expect: 100-continue before uploading a large request body. The server's interim response tells it to continue; the client still waits for the final response after sending the body.

How to read this response

1. Find the status line in your browser's Network panel, API client, or server access log.
2. Read the response body and headers shown above; headers such as Location, Allow, Retry-After, and WWW-Authenticate explain the next step.
3. Use the code's class to orient your diagnosis: informational, successful, redirected, request-related, or server-side.

How to check a status code

Enter a URL in the HTTP Status Checker to see its status code, every redirect hop, and response time. For redirect-heavy pages, the Website Speed Test shows how much time redirects add.

Frequently asked questions

What it means: HTTP 100

100 Continue: The server received the request headers and the client should send the request body.

Common causes: 100

The client sent an Expect: 100-continue header. A large upload is being negotiated before the body is sent.

How to fix it: HTTP 100

No action is needed; the final status follows after the body is sent. If uploads stall, check that proxies forward 100 Continue correctly.

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