When an origin server responds to a browser request, it returns an HTTP status code. When a user agent visits a website, their browser sends a request to the server. The origin web server then responds to the browser request with a three-digit code, known as the HTTP Status Code. The first digit of the status code indicates the class of the response.
These response codes act as a communication mechanism between the origin server and the browser, indicating whether the request was successful or encountered an issue. Understanding HTTP status codes is essential for diagnosing errors and ensuring smooth website functionality. Some of these status codes also help search engines provide better access to user-agent sites.
For example:
- A 301 Redirect permanently redirects users and bots to a new page location.
- A 400 Bad Request indicates that the original request was malformed or contained invalid syntax, preventing successful processing.
These status codes are displayed in the message body of the HTTP response and are important for website maintenance, as search engines favor well-maintained sites.
What are the different HTTP status codes?
Below are some common HTTP status codes that indicate different types of server responses.
2xx Success Codes:
- 200 (OK):The request was successful, and the server returned the requested data.
- 201 (Created):The request was successful, and a new resource was created.
- 202 (Accepted):The request has been accepted for processing, but the process is not yet complete.
- 206 (Partial Content):The server is returning only part of the requested resource.
- 207 (Multi-Status):A response containing multiple status codes, commonly used for WebDAV.
- 208 (Already Reported):Indicates that a particular resource has already been reported in the current context (used in WebDAV).
- 226 (IM Used):The server successfully processed the request, but the response includes instance manipulations (IM).
3xx Status Codes:
- 300 (Multiple Choices):The requested resource has multiple options, and the user must choose one.
- 305 (Use Proxy):The requested resource must be accessed through a proxy server.
- 306 (Unused):Previously used but now reserved for future use.
- 308 (Permanent Redirect):The resource has been permanently moved, and future requests should be sent to the new location.
4xx Status Codes:
- 402 (Payment Required):Payment is required to access the requested resource.
- 404 (Not Found):The requested resource could not be found on the server.
- 411 (Length Required):The request is missing the required Content-Length header, so the server refuses to process it.
- 421 (Misdirected Request):The request was directed to the wrong server, which cannot process it.
- 423 (Locked):The requested resource is locked and cannot be accessed without modification.
5xx Status Codes:
- 502 (Bad Gateway):The server, acting as a gateway or proxy, received an invalid response from the upstream server.
- 503 (Service Unavailable):The server is temporarily unavailable due to maintenance or high traffic.
- 508 (Loop Detected):The server detected an infinite loop while processing the request.
- 599 (Network Connection Timeout Error):A non-standard status code used by some proxies to indicate a network timeout.
What is a request method and a request header field?
A request method specifies the action that the client wants the server to perform. Common request methods include:
- GET:Retrieve a resource.
- POST:Create a new resource.
- PUT:Update an existing resource.
- DELETE:Remove a resource.
Request Header Fields:
Request headers provide additional information about the request, enhancing communication between the client and server. These headers help the server understand how to handle the request.
If request headers are misconfigured, they can lead to invalid requests or incorrect request routing. Keeping headers properly formatted and updated ensures smooth server communication. In future requests, the client may need to add updated range headers to correctly handle response content.
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