### 400 - Bad Request The request was incorrect or missing something, so the server couldn’t understand it. Example: Submitting a form with incomplete or invalid data. ### 401 - Unauthorized The request is missing proper authentication. Example: Trying to access an account without logging in. ### 403 - Forbidden You’re authenticated but don’t have permission to access this resource. Example: Trying to open a document that you don’t have access to. ### 404 - Not Found The requested resource doesn’t exist. Example: Clicking a broken link or mistyping a URL. ### 500 - Internal Server Error Something went wrong on the server’s side, but it’s not your fault. Example: The system crashes unexpectedly. ### 501 - Not Implemented The server doesn’t support the requested action. Example: Trying to use a feature that hasn’t been built yet. ### 502 - Bad Gateway The server acting as a middleman (gateway) got an invalid response from another server. Example: A temporary issue when a service provider is down. ### 503 - Service Unavailable The server is temporarily unable to handle the request, often due to high traffic or maintenance. Example: A website is overloaded with visitors. ### 504 - Gateway Timeout The server acting as a middleman (gateway) took too long to get a response from another server. Example: A slow network causing a timeout. --- ## References - [HTTP response status codes - HTTP | MDN](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status#client_error_responses)