Status codes communicate intent instantly.

Common codes:

• 200 OK - Success
• 201 Created - Resource created
• 204 No Content - Success, no body (DELETE)
• 400 Bad Request - Client error (validation)
• 401 Unauthorized - No/invalid auth
• 403 Forbidden - Auth valid but not allowed
• 404 Not Found - Resource does not exist
• 500 Internal Error - Server bug