HTTP Status 401 - Unauthorized

GET /api/users/me HTTP/1.1
Host: api.example.com

HTTP/1.1 401 Unauthorized
WWW-Authenticate: Bearer realm="API", error="missing_token"
Content-Type: application/json

{"error": "authentication_required", "message": "Authorization header missing"}

GET /api/protected HTTP/1.1
Host: api.example.com
Authorization: Bearer eyJhbGc...expired_token

HTTP/1.1 401 Unauthorized
WWW-Authenticate: Bearer realm="API", error="invalid_token", error_description="Token expired"
Content-Type: application/json

{"error": "token_expired", "message": "JWT expired at 2025-10-01T10:00:00Z"}

GET /api/data HTTP/1.1
Host: api.example.com
X-API-Key: invalid_key_123

HTTP/1.1 401 Unauthorized
WWW-Authenticate: X-API-Key realm="API"
Content-Type: application/json

{"error": "invalid_credentials", "message": "API key not found or revoked"}