Understanding Response Status Codes :A complete guide

HTTP response status codes are used to communicate the result of a server’s attempt to process a request. These codes are categorized into five classes based on the first digit of the code. Here’s a breakdown of each category and the meaning of common status codes:

1xx: Informational Responses – Response Status Codes

These status codes indicate that the request has been received and the process is continuing. They are rarely seen in normal use, but they do have a purpose in certain protocols.

• 100 Continue
  The server has received the request headers, and the client should proceed to send the request body.
• 101 Switching Protocols
  The server is switching protocols as requested by the client (e.g., upgrading from HTTP/1.1 to WebSocket).
• 102 Processing (WebDAV)
  The server is processing the request but has not yet completed it.

2xx: Successful Responses

These codes indicate that the request has been successfully received, understood, and processed by the server.

• 200 OK
  The request was successful, and the server returned the requested data (for GET) or confirmed the request (for POST, PUT, DELETE, etc.).
• 201 Created
  The request was successful and resulted in the creation of a new resource (typically used with POST requests).
• 202 Accepted
  The request has been accepted for processing, but the processing has not been completed. This doesn’t guarantee that the request will be completed.
• 204 No Content
  The request was successful, but there is no content to return. Often used for DELETE requests.
• 205 Reset Content
  The server has fulfilled the request and the client should reset the document view.
• 206 Partial Content
  The server is sending only part of the resource, typically used for partial downloads (e.g., with the Range header).

3xx: Redirection Response Status Codes

These codes indicate that further action is needed by the client to complete the request, often because the requested resource has moved.

• 300 Multiple Choices
  The request has more than one possible response. The client can choose which resource to follow.
• 301 Moved Permanently
  The resource has permanently moved to a new URL. The client should use the new URL in future requests.
• 302 Found (Previously “Moved Temporarily”)
  The resource has been temporarily moved to a different URL. The client should continue to use the original URL for future requests.
• 303 See Other
  The response to the request can be found under a different URL, using the GET method.
• 304 Not Modified
  The resource has not been modified since the last request. The client can use the cached version of the resource.
• 307 Temporary Redirect
  The resource is temporarily located at a different URL, but future requests should still use the original URL.
• 308 Permanent Redirect
  The resource has been permanently moved to a new URL, and future requests should use this URL.

4xx: Client Error Response Status Codes

These status codes indicate that there was a problem with the request made by the client (the user or the client application).

• 400 Bad Request
  The server cannot process the request because of malformed syntax or invalid data.
• 401 Unauthorized
  The request lacks proper authentication credentials (e.g., missing or invalid API key, token, or login credentials).
• 402 Payment Required
  This code is reserved for future use; however, it may be used for payment-related issues.
• 403 Forbidden
  The server understood the request but refuses to authorize it. This is different from 401 (Unauthorized) because it indicates that authentication was successful, but the server denies access.
• 404 Not Found
  The server cannot find the requested resource. The URL may be incorrect, or the resource does not exist.
• 405 Method Not Allowed
  The HTTP method used is not allowed for the resource (e.g., trying to POST to a read-only resource).
• 406 Not Acceptable
  The server cannot generate a response that is acceptable according to the Accept headers sent in the request.
• 407 Proxy Authentication Required
  The client must authenticate with a proxy server before making the request.
• 408 Request Timeout
  The server timed out waiting for the request from the client. This can happen when the client takes too long to send data.
• 409 Conflict
  The request could not be completed due to a conflict with the current state of the resource (e.g., attempting to create a duplicate resource).
• 410 Gone
  The resource is no longer available and has been permanently removed from the server.
• 411 Length Required
  The request did not specify the Content-Length header, which is required by the server.
• 412 Precondition Failed
  One of the conditions in the If-* headers (e.g., If-Match, If-None-Match) failed.
• 413 Payload Too Large
  The request entity is larger than the server is willing or able to process (e.g., uploading a very large file).
• 414 URI Too Long
  The URL requested by the client is too long for the server to process.
• 415 Unsupported Media Type
  The server cannot process the request because the content type is not supported.
• 416 Range Not Satisfiable
  The server cannot fulfill the range request (e.g., requested byte range is beyond the file size).
• 417 Expectation Failed
  The server cannot meet the expectations specified in the Expect header.
• 418 I’m a teapot
  This is a joke status code defined in the Hyper Text Coffee Pot Control Protocol (RFC 2324). It’s not used in real-world applications.
• 422 Unprocessable Entity (WebDAV)
  The server understands the content type of the request entity, but it is unable to process the contained instructions (e.g., semantic errors).
• 429 Too Many Requests
  The user has sent too many requests in a given amount of time (“rate limiting”).

5xx: Server Error Responses

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

• 500 Internal Server Error
  A generic error message when the server encounters an unexpected condition that prevents it from fulfilling the request.
• 501 Not Implemented
  The server does not support the functionality required to fulfill the request (e.g., the server does not support the HTTP method).
• 502 Bad Gateway
  The server received an invalid response from an upstream server while processing the request (typically in a proxy or gateway setup).
• 503 Service Unavailable
  The server is temporarily unable to handle the request (e.g., due to being overloaded or down for maintenance).
• 504 Gateway Timeout
  The server did not receive a timely response from an upstream server or some other auxiliary server.
• 505 HTTP Version Not Supported
  The server does not support the HTTP protocol version that was used in the request.
• 507 Insufficient Storage (WebDAV)
  The server is unable to store the representation needed to complete the request.
• 510 Not Extended
  The server requires further extensions to fulfill the request.

Summary of Key Status Codes

These status codes give a lot of insight into what is going on with an HTTP request and response, helping developers debug and manage server-client communication efficiently. You can test your APIs by using Postman, HTTPie, Hoppscotch

Other Keywords

• Which API is Faster?
• How to learn Node JS in 30 days
• How to create Database migration in node js