Master HTTP Status Codes: A Complete Cheat‑Sheet for Developers

Whenever a client sends a request to a server, the response always includes a status code. Users may not see it, but developers can view it via packet capture; it is returned on every client‑server interaction.

Even non‑programmers may recognize the 404 Not Found error.

In this article we discuss everything about HTTP and its response status codes, serving as a handy reference whenever you encounter them.

What this article covers

1. What is HTTP? 2. What are status codes? 3. 1XX – Informational codes 4. 2XX – Success codes 5. 3XX – Redirection codes 6. 4XX – Client error codes 7. 5XX – Server error codes

What is HTTP?

HTTP stands for Hypertext Transfer Protocol. According to Wikipedia:

Hypertext Transfer Protocol is an application‑layer protocol for distributed, collaborative, hypermedia information systems.

HTTP is a client‑server protocol that underlies any data exchange on the Web. Each interaction between client and server is called a message, which can be a request or a response. The client sends an HTTP request, and the server replies with an HTTP response.

What are status codes?

For every client request, the server responds with a code that conveys the request’s status, allowing a quick check of success without inspecting the response body.

These codes consist of three digits, grouped into five standard classes identified by the first digit:

1XX – Informational

2XX – Success

3XX – Redirection

4XX – Client error

5XX – Server error

Below is a brief overview of each class and the most common codes.

1XX – Informational responses

Informational responses indicate that the request has been received and understood and that processing is continuing.

100 – Continue: Server has received the request headers and the client should continue sending the request body.

101 – Switching Protocols: The requester asks the server to switch protocols, and the server agrees.

102 – Processing: The server has received and is processing the request but no response is yet available.

103 – Early Hints: Used to return some response headers before the final HTTP message.

2XX – Success

These codes indicate that the client’s request was successfully received, understood, and accepted.

200 – OK: Standard response for successful HTTP requests.

201 – Created: The request has been fulfilled and resulted in a new resource being created.

202 – Accepted: The request has been accepted for processing, but the processing has not been completed.

204 – No Content: The server successfully processed the request and is not returning any content.

3XX – Redirection

This class indicates that further action must be taken by the client to complete the request.

301 – Moved Permanently: The URL has been permanently moved to a new location.

305 – Use Proxy: The requested resource must be accessed through the proxy given by the response.

307 – Temporary Redirect: The resource resides temporarily under a different URI.

4XX – Client error

These codes indicate that the error seems to have been caused by the client.

400 – Bad Request: The server cannot or will not process the request due to a client error.

401 – Unauthorized: Authentication is required and has failed or has not yet been provided.

403 – Forbidden: The server understood the request but refuses to authorize it.

404 – Not Found: The requested resource could not be found.

405 – Method Not Allowed: The request method is known by the server but is not supported by the target resource.

414 – URI Too Long: The URI provided was too long for the server to process.

429 – Too Many Requests: The user has sent too many requests in a given amount of time.

5XX – Server error

These codes indicate that the server failed to fulfill a valid request.

500 – Internal Server Error: A generic error message when no more specific message is suitable.

501 – Not Implemented: The server does not support the functionality required to fulfill the request.

502 – Bad Gateway: The server, while acting as a gateway, received an invalid response from the upstream server.

503 – Service Unavailable: The server is not ready to handle the request, often due to overload or maintenance.

This concludes the entire content of the article.