← All Status Codes
400
Bad Request
⚠️ Client Error
Low Risk
📖 What Is HTTP 400?
The server cannot process the request due to malformed syntax, invalid request framing, or deceptive request routing.
🛡️ Security Implications
Often triggered by security scanners and attack attempts. A high volume of 400 errors may indicate active scanning or fuzzing.
🔍 Common Causes
Malformed JSON/XML body, missing required parameters, invalid URL encoding, oversized headers, or corrupted request.
🔧 How to Fix
Check request format and encoding. Validate Content-Type matches the body format. Check for special characters in URLs.
🖥️ How to Check
curl -I -o /dev/null -w "%{http_code}" https://example.com