← All Status Codes
411
Length Required
⚠️ Client Error
Low Risk
📖 What Is HTTP 411?
The server refuses the request because the Content-Length header is missing. Required for requests with a body.
🛡️ Security Implications
Servers should require Content-Length to prevent HTTP request smuggling attacks that exploit ambiguous message lengths.
🔍 Common Causes
Client did not send Content-Length header with a POST/PUT request. Chunked transfer encoding not accepted.
🔧 How to Fix
Include the Content-Length header in requests with a body. Calculate the exact byte length of the request body.
🖥️ How to Check
curl -I -o /dev/null -w "%{http_code}" https://example.com