In this tutorial, we will show you how to use the Curl tool through practical examples and detailed explanations of the most common curl options. What is Curl? Curl is command line utility for transferring data from or to a server designed to work without user interaction. With curl you can download or upload data using one of the supported protocols including HTTP, HTTPS, SCP, SFTP and FTP. Curl provides a number of options allowing you to resume transfers, limit the bandwidth, proxy support, user authentication and much more.