Is it mandatory to include transmitted data in a POST request only in the request body?

No, data in a POST request does not necessarily have to be sent only in the request body. Although the body is typically used for transmitting large or structured data (like JSON), parameters can also be sent in the URL (query string) or headers.

However, according to HTTP standards, parameters affecting the request action are better sent in the body for POST requests to avoid URL length limitations and improve security.

Example: you can send a POST request with parameters in the URL, but this is not recommended for sensitive data.