HTTP 411 Length Required — Missing Content-Length Header

Overview

HTTP 411 Length Required means the server refuses the request because the Content-Length header is missing and the server requires it.

Key Details

• Server requires the Content-Length header but the client did not send it
• Common with POST and PUT requests that have a request body
• Some servers and proxies require Content-Length for security and resource allocation
• Chunked transfer encoding (Transfer-Encoding: chunked) may not be accepted
• Load balancers and WAFs frequently enforce Content-Length requirements

Common Causes

• HTTP client not setting Content-Length header on POST/PUT requests
• Using chunked transfer encoding against a server that does not support it
• Proxy or WAF stripping the Content-Length header from requests
• Streaming request body without pre-calculating total size

Steps

1. 1Add Content-Length header to your request matching the body size in bytes
2. 2In curl, use -H 'Content-Length: N' or let curl calculate it automatically with -d
3. 3If using chunked encoding, switch to buffered body with explicit Content-Length
4. 4Check if a proxy or CDN is modifying request headers in transit
5. 5For large uploads, check if the server supports chunked encoding or requires Content-Length

Tags

More in 4xx Client Error

Frequently Asked Questions