What it means

A 411 Length Required response means the server refused to process the request because the Content-Length header was missing. Some servers require this header to know how much data to expect.

Common causes

• The request did not include a Content-Length header.
• The server is strict about header requirements.

How to fix it

• Include the Content-Length header in the request.
• Most HTTP libraries set this automatically, so check that the request is being constructed correctly.