ErrorFindly
1001xx InformationalInfo

HTTP 100 Continue

Defined in RFC 7231

What Does HTTP 100 Mean?

The server has received the request headers and the client should proceed to send the request body.

Common Causes

  1. 1Client sending large request body with Expect: 100-continue header
  2. 2Server acknowledging initial part of a request
  3. 3Intermediary proxy forwarding preliminary response

Impact

  • ⚠No visible impact — this is an interim response
  • ⚠Request continues processing normally

Developer Fix

For web developers and application engineers

  1. 1No action needed — this is normal HTTP behavior
  2. 2Ensure client libraries handle 100 Continue properly
  3. 3Use Expect header for large uploads to avoid wasted bandwidth

Server Admin Fix

For system administrators and DevOps engineers

  1. 1Verify server supports Expect: 100-continue properly
  2. 2Check proxy configurations for proper 1xx forwarding

Frequently Asked Questions

Do I need to handle 100 Continue in my app?
Most HTTP client libraries handle 100 Continue automatically. You typically only need to worry about it if you're building a custom HTTP client or dealing with large file uploads.
Can 100 Continue cause problems?
Some older proxies and servers don't handle 100 Continue correctly, which can cause timeouts. If you experience issues, try disabling the Expect header in your client.

Related HTTP Status Codes

200OK

About the Author

Web Infrastructure Team

Verified against official RFC specifications and real-world server configurations. HTTP status code behavior confirmed across Apache, Nginx, and Cloudflare.