The protocol used for transferring files over the internet is the File Transfer Protocol, or FTP. It is an application-layer protocol that lets a client upload, download, rename, and manage files on a remote server.
FTP originated in the early ARPANET era. Abhay Bhushan wrote its original specification, published in 1971, making FTP one of the internet’s older protocols. It uses separate control and data connections; the familiar control port is 21, while traditional active-mode data transfers use port 20.
FTP is often confused with HTTP, which primarily delivers web pages and other web resources, and SMTP, which transfers email between mail servers. TCP is different again: it is a transport protocol that FTP can use to provide reliable communication.
Traditional FTP sends usernames, passwords, and file contents without encryption. For safer modern transfers, administrators commonly use FTPS, which adds TLS, or SFTP, which is a separate file-transfer system built over SSH. Major browsers removed built-in FTP support in the early 2020s, but FTP remains important in server administration and automated workflows.