HTTP Methods and Common Error Codes
Tags: api, webdev, website, microservices
Published: 2024-06-25 13:21:46

Understanding HTTP methods and error codes is crucial for anyone involved in web development or interacting with web services. By grasping the purpose and implications of each method and common error codes, developers can build more robust applications, diagnose and troubleshoot issues effectively, and ensure seamless communication between clients and servers on the web.

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## HTTP Methods
HTTP methods such as **GET, POST, PUT, DELETE, PATCH, OPTIONS, and HEAD** dictate what actions clients can perform on server resources. Each method serves a specific purpose, from retrieving data to modifying existing resources or checking server capabilities.

| **HTTP Method** | **Purpose**                    | **Use Case**                                                         |
| --------------- | ------------------------------ | -------------------------------------------------------------------- |
| **GET**         | Retrieve data                  | Fetch a list of users or a specific user’s details.                  |
| **POST**        | Create a new resource          | Add a new user to the database.                                      |
| **PUT**         | Update or create resource      | Update an existing user's information or create if it doesn’t exist. |
| **DELETE**      | Remove a resource              | Remove a user from the database.                                     |
| **PATCH**       | Partially update a resource    | Update only the email address of a user.                             |
| **OPTIONS**     | Retrieve communication options | Check which HTTP methods are supported by the server for a resource. |
| **HEAD**        | Retrieve headers only          | Get metadata about a list of users without the actual user data.     |

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## Common HTTP Error Codes
HTTP error codes provide insight into the outcome of a client's request. They range from indicating successful requests (like 200 OK) to various types of client and server errors (such as 404 Not Found or 500 Internal Server Error), helping diagnose issues encountered during web interactions.

| **Error Code** | **Description**                                                    | **Use Case**                                                        |
| -------------- | ------------------------------------------------------------------ | ------------------------------------------------------------------- |
| **400**        | Bad Request: Invalid syntax.                                       | Client sends a malformed request to the server.                     |
| **401**        | Unauthorized: Authentication required.                             | Client tries to access a protected resource without authentication. |
| **403**        | Forbidden: Access denied.                                          | Client lacks permission to access a specific resource.              |
| **404**        | Not Found: Resource not found.                                     | Requested resource does not exist on the server.                    |
| **500**        | Internal Server Error: Server encountered an unexpected condition. | Server error due to an unhandled exception or misconfiguration.     |
| **502**        | Bad Gateway: Invalid response from an upstream server.             | Proxy server receives an invalid response from an upstream server.  |
| **503**        | Service Unavailable: Server is not ready to handle the request.    | Server is down for maintenance or is overloaded.                    |

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## Conclusion
In conclusion, understanding HTTP methods and common error codes is fundamental for anyone involved in web development or API design. By mastering these concepts, developers can optimise their applications for efficiency, reliability, and user experience.