API testing is essential to ensure that software applications work correctly. One key aspect of API testing is understanding and interpreting HTTP response codes. This article will discuss the world of response codes, exploring the different categories and their significance. By the end, you will completely understand response codes as they relate to API testing.
Table of contents
- What are HTTP response codes?
- Informational response codes (1xx)
- Success response codes (2xx)
- Redirection response codes (3xx)
- Client error response codes (4xx)
- Server error response codes (5xx)
What are HTTP response codes?
Response codes, or HTTP status codes, are three-digit numbers that tell us what happens when a client sends a request to a server. They indicate whether a request was successful, encountered an error, or requires further action. Each code falls into one of five categories: informational, success, redirection, client error, or server error.
Informational response codes (1xx)
Informational response codes mean that the server has received the request and is currently working on processing it. These codes are primarily used for diagnostic purposes and are rarely encountered in API testing. Some standard informational response codes include:
- 100 Continue: The server acknowledges the client’s initial request and expects further action.
- 101 Switching Protocols: The server informs the client about the requested protocol switch.
- 102 Processing: The server is processing the request but still needs to finish it.
- 103 Early Hints: The server provides some response headers before the final response.
Success response codes (2xx)
Success response codes indicate that the server has received, understood, and processed the client’s request. These codes signify that everything went as expected. Some commonly encountered success response codes include:
- 200 OK: The request was successful, and the server now provides the requested data to the client.
- 201 Created: The server has successfully created a new resource based on the client’s request.
- 204 No Content: The server has processed the request but has no content to return.
- 206 Partial Content: The server successfully fulfilled a partial GET request.
Redirection response codes (3xx)
Redirection response codes indicate that further action is needed to complete the request. These codes are commonly encountered when dealing with URLs or when the client’s requested resource has moved. Some frequently experienced redirection response codes include:
- 301 Moved Permanently: The requested resource has permanently moved to a new URL.
- 302 Found: The requested resource temporarily resides under a different URL.
- 303 See Other: The server directs the client to a different URL to retrieve the response.
- 307 Temporary Redirect: The server temporarily redirects the client to a different URL.
- 308 Permanent Redirect: The server permanently redirects the client to a different URL.
Client error response codes (4xx)
Client error response codes indicate that the client’s request cannot be fulfilled due to an error on the client’s side. These codes often require action from the client to resolve the issue. Some commonly encountered client error response codes include:
- 400 Bad Request: The server cannot process the client’s request due to a malformed syntax or invalid parameters.
- 401 Unauthorized: The client must authenticate itself before accessing the requested resource.
- 403 Forbidden: The client has no permission to access the requested resource.
- 404 Not Found: The requested resource was unavailable on the server.
- 405 Method Not Allowed: The requested method (GET, POST, PUT, etc.) is not allowed for the given resource.
Server error response codes (5xx)
Server error response codes indicate that the server encountered an error while processing the client’s request. These codes are usually temporary and require attention from the server administrator. Some commonly encountered server error response codes include:
- 500 Internal Server Error: The server encountered an unexpected condition that prevented it from fulfilling the request.
- 501 Not Implemented: The server does not support the functionality required to fulfill the request.
- 502 Bad Gateway: The server acts as a gateway or proxy and receives an invalid response status from the upstream server.
- 503 Service Unavailable: The server is temporarily unable to handle the request due to maintenance or overload.
- 504 Gateway Timeout: The server, which acts as a gateway or proxy, didn’t receive a response from the upstream server within the expected time.
Final thoughts HTTP response codes in API testing
Response codes are an integral part of API testing as they provide valuable information about the outcome of a client’s request. Understanding the different categories of response codes, such as informational, success, redirection, client error, and server error, is essential for effective API testing. By familiarizing yourself with these codes and their meanings, you can troubleshoot issues and ensure the reliability and functionality of the software applications you work with. Remember that each response code carries its significance, enabling you to identify and address any potential issues that may arise during API testing.
This post is part of our comprehensive Postman Mini-Course.
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