← All Status Codes
401
Unauthorized
⚠️ Client Error
High Risk
📖 What Is HTTP 401?
Authentication is required and has either failed or not been provided. The response must include a WWW-Authenticate header indicating the auth scheme.
🛡️ Security Implications
Brute force target. Implement rate limiting, account lockout, and CAPTCHA. Never reveal whether the username or password was incorrect.
🔍 Common Causes
Missing, expired, or invalid authentication token/credentials. Session timeout. API key not provided.
🔧 How to Fix
Provide valid credentials. Check token expiration. Implement proper session management with refresh tokens.
🖥️ How to Check
curl -I -o /dev/null -w "%{http_code}" https://example.com