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Understanding HTTP Status Codes: A Guide for Developers


In the vast expanse of the internet, communication between web servers and clients is governed by a protocol known as HTTP (Hypertext Transfer Protocol). Central to this protocol are HTTP status codes, which indicate the result of a client’s request to a server.

Understanding these codes is crucial for developers and IT professionals as they diagnose issues, optimize user experiences, and ensure the seamless operation of web applications.

HTTP Status Code

1xx Informational Responses

These codes represent temporary responses that inform the client that the request has been received and the process is continuing.

  • 100 Continue: Encourages the client to proceed with its request
  • 101 Switching Protocols: Acknowledges request to switch protocols
  • 102 Processing: Indicates the server is processing the request but no response is available yet

2xx Success

Success codes confirm that a request was successfully received, understood, and accepted.

  • 200 OK: The standard response for successful requests
  • 201 Created: Indicates a resource was successfully created
  • 202 Accepted: The request has been accepted for processing, but the processing has not been completed.
  • 204 No Content: The request was successful but there’s no content to send back
  • 206 Partial Content: The server is delivering only part of the resource due to a range header sent by the client.

3xx Redirection

Redirection codes tell the client that further action needs to be taken by the user agent in order to fulfill the request.

  • 301 Moved Permanently: The requested resource has been moved to a new URL permanently
  • 302 Found: Temporarily redirects to another resource
  • 304 Not Modified: Indicates the resource has not been modified since last requested
  • 307 Temporary Redirect: The requested resource resides temporarily under a different URI.

4xx Client Error

These status codes are returned when the server believes the client has erred.

  • 400 Bad Request: The server cannot process the request due to client error
  • 401 Unauthorized: Authentication is required and has failed or has not yet been provided
  • 403 Forbidden: The server understood the request, but it refuses to authorize it.
  • 404 Not Found: The server can’t find the requested resource
  • 405 Method Not Allowed: A request method is not supported for the requested resource.

5xx Server Error

Server error responses indicate that the request was valid, but the server failed to fulfill it.

  • 500 Internal Server Error: A generic error message when an unexpected condition was encountered
  • 502 Bad Gateway: The server received an invalid response from the upstream server
  • 503 Service Unavailable: The server is not ready to handle the request
  • 504 Gateway Timeout: The server was acting as a gateway or proxy and did not receive a timely response from the upstream server.

Special Mention

  • 418 I’m a teapot: A humorous code indicating the server refuses to brew coffee because it is, permanently, a teapot.
  • 451 Unavailable For Legal Reasons: A server operator has received a legal demand to deny access to a resource or to a set of resources that includes the requested resource.


HTTP status codes are a critical part of web development and maintenance. They provide immediate feedback about the interaction between the client and server, offering insights into what went wrong and how to fix it. By understanding these codes, developers and IT professionals can troubleshoot issues more effectively, enhance the user experience, and maintain the health of web applications.

Remember, while these codes are standardized, their interpretation can slightly vary between web servers and applications. Always consult the documentation of the specific technologies you are working with for the most accurate information.

This structure provides a comprehensive overview of HTTP status codes, categorizing them by their classes and offering explanations for each. Feel free to adjust the content to better fit your audience’s knowledge level or specific interests.



About Author

As Neelabh Singh, I am a Senior Software Engineer with 6.6 years of experience, specializing in Java technologies, Microservices, AWS, Algorithms, and Data Structures. I am also a technology blogger and an active participant in several online coding communities.

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