HTTP Response Codes: A Comprehensive Guide for Software Testers

HTTP Response Codes: A Comprehensive Guide for Software Testers

In the realm of web development and API testing, understanding HTTP response codes is crucial. These status codes are issued by a server in response to a client’s request made to the server. They are an essential part of the web’s protocol and help developers and testers to understand what is happening with their requests. Here, we present a detailed guide to HTTP response codes, categorized for ease of understanding.

1xx Informational Responses

• 100 Continue: The server has received the request headers, and the client should proceed to send the request body.
• 101 Switching Protocols: The requester has asked the server to switch protocols and the server is acknowledging that it will do so.
• 102 Processing: The server has received and is processing the request, but no response is available yet.

2xx Successful Responses

• 200 OK: The request has succeeded. The meaning of the success depends on the HTTP method.
• 201 Created: The request has been fulfilled, resulting in the creation of a new resource.
• 202 Accepted: The request has been accepted for processing, but the processing has not been completed.
• 203 Non-Authoritative Information: The request was successful but the information in the response is from a local or third-party copy, not from the server.
• 204 No Content: The server successfully processed the request, and is not returning any content.
• 205 Reset Content: The server successfully processed the request, asks that the requester reset the document view.
• 206 Partial Content: The server is delivering only part of the resource due to a range header sent by the client.

3xx Redirection Messages

• 300 Multiple Choices: The request has more than one possible response. The user or user agent should choose one of them.
• 301 Moved Permanently: The URL of the requested resource has been changed permanently. The new URL is given in the response.
• 302 Found: The URI of the requested resource has been changed temporarily. Further changes in the URI might be made in the future.
• 303 See Other: The response to the request can be found under another URI using the GET method.
• 304 Not Modified: Indicates that the resource has not been modified since the version specified by the request headers.
• 305 Use Proxy: The requested resource is available only through a proxy, whose address is provided in the response.
• 307 Temporary Redirect: The request should be repeated with another URI, but future requests should still use the original URI.
• 308 Permanent Redirect: The request, and all future requests should be repeated using another URI.

4xx Client Error Responses

• 400 Bad Request: The server cannot or will not process the request due to a client error (e.g., malformed request syntax).
• 401 Unauthorized: The request requires user authentication.
• 402 Payment Required: Reserved for future use. Initially created for digital payment systems.
• 403 Forbidden: The server understood the request, but refuses to authorize it.
• 404 Not Found: The server cannot find the requested resource.
• 405 Method Not Allowed: The request method is known by the server but is not supported by the target resource.
• 406 Not Acceptable: The server cannot produce a response matching the list of acceptable values defined in the request’s headers.
• 407 Proxy Authentication Required: The client must first authenticate itself with the proxy.
• 408 Request Timeout: The server did not receive a complete request message within the time that it was prepared to wait.
• 409 Conflict: The request could not be completed due to a conflict with the current state of the resource.
• 410 Gone: The resource requested is no longer available and will not be available again.
• 411 Length Required: The request did not specify the length of its content, which is required by the requested resource.
• 412 Precondition Failed: The server does not meet one of the preconditions that the requester put on the request.
• 413 Payload Too Large: The request is larger than the server is willing or able to process.
• 414 URI Too Long: The URI provided was too long for the server to process.
• 415 Unsupported Media Type: The request entity has a media type which the server or resource does not support.
• 416 Range Not Satisfiable: The client has asked for a portion of the file (byte serving), but the server cannot supply that portion.
• 417 Expectation Failed: The server cannot meet the requirements of the Expect request-header field.
• 418 I’m a teapot: This code was defined in 1998 as one of the traditional IETF April Fools’ jokes.
• 421 Misdirected Request: The request was directed at a server that is not able to produce a response.
• 422 Unprocessable Entity: The request was well-formed but was unable to be followed due to semantic errors.
• 423 Locked: The resource that is being accessed is locked.
• 424 Failed Dependency: The request failed due to failure of a previous request.
• 426 Upgrade Required: The client should switch to a different protocol such as TLS/1.0.
• 428 Precondition Required: The origin server requires the request to be conditional.
• 429 Too Many Requests: The user has sent too many requests in a given amount of time (“rate limiting”).
• 431 Request Header Fields Too Large: The server is unwilling to process the request because its header fields are too large.
• 451 Unavailable For Legal Reasons: The user-agent requested a resource that cannot legally be provided.

5xx Server Error Responses

• 500 Internal Server Error: A generic error message, given when an unexpected condition was encountered.
• 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 or proxy, received an invalid response from the upstream server.
• 503 Service Unavailable: The server is not ready to handle the request. Common causes are a server that is down for maintenance or that is overloaded.
• 504 Gateway Timeout: The server was acting as a gateway or proxy and did not receive a timely response from the upstream server.
• 505 HTTP Version Not Supported: The server does not support the HTTP protocol version used in the request.
• 506 Variant Also Negotiates: Transparent content negotiation for the request results in a circular reference.
• 507 Insufficient Storage: The server is unable to store the representation needed to complete the request.
• 508 Loop Detected: The server detected an infinite loop while processing a request.
• 510 Not Extended: Further extensions to the request are required for the server to fulfill it.
• 511 Network Authentication Required: The client needs to authenticate to gain network access.

Conclusion

Understanding HTTP response codes is vital for software testers as it helps in diagnosing issues, debugging, and ensuring that web applications and APIs function as expected. This comprehensive guide provides a quick reference to all the response codes, aiding in better testing and troubleshooting processes. Keeping this guide handy will ensure that you can quickly identify and resolve any issues related to HTTP response codes in your projects.