HTTP Status Codes

HTTP status codes are standard responses returned by a server to indicate the result of a client’s request. They help developers understand whether a request was successful, redirected, or failed.

• Status codes are grouped into five categories: 1xx, 2xx, 3xx, 4xx, and 5xx.
• They are essential for API testing, debugging, and error handling.
• Each code provides clear communication between the client and the server.

HTTP Status Code Categories

HTTP status codes are grouped into five categories, with each category representing a different type of response from the server.

1xx – Informational Response

These codes indicate that the server has received the request and is continuing to process it.

Example : 100 Continue - The client can continue sending the request.

2xx – Success Response

These codes indicate that the request was successfully received and processed.

Examples:

• 200 OK - Request completed successfully.
• 201 Created - A new resource was successfully created.
• 204 No Content - Request was successful, but there is no response body.

3xx – Redirection Response

These codes indicate that the client needs to take additional action, such as using a different URL or cached resource.

Examples:

• 301 Moved Permanently - Resource has permanently moved to a new URL.
• 302 Found - Resource is temporarily available at another URL.
• 304 Not Modified - Cached resource can be used because it has not changed.

4xx – Client Error Response

These codes indicate that the request cannot be fulfilled because of an issue with the client's request.

Examples:

• 400 Bad Request – Request contains invalid data or syntax.
• 401 Unauthorised – Authentication is required or invalid.
• 403 Forbidden - Server understood the request but refuses access.
• 404 Not Found – Requested resource could not be found.
• 429 Too many Requests - Client has sent too many requests in a given period.

5xx – Server Error Response

These codes indicate that the server encountered an error while processing a valid request.

Examples:

• 500 Internal Server Error – Unexpected error occurred on the server.
• 502 Bad Gateway - Server received an invalid response from an upstream server.
• 503 Service Unavailable – Server is temporarily unavailable.
• 504 Gateway Timeout - Server did not receive a timely response from an upstream server.

Common HTTP Status Codes

APIs commonly use a set of HTTP status codes to communicate the outcome of a request. The following codes are frequently used in API development and testing.