Glossary

FTP

Definition: File Transfer Protocol is a standard network protocol used to transfer files between a client and a server over a TCP/IP network.

FTP (File Transfer Protocol) is one of the oldest internet protocols, defined in RFC 959 (1985). It is used to transfer files between a client (your computer) and a server. Web developers traditionally used FTP to upload website files to their hosting server.

How FTP Works

  • FTP uses two separate TCP connections: a control channel (port 21) for commands and a data channel (port 20 or negotiated) for file transfers.
  • The client authenticates with a username and password.
  • Files can be uploaded, downloaded, renamed, deleted and listed.

FTP Security Problem

Plain FTP transmits all data — including credentials — in clear text. Anyone who can intercept the network traffic can read the username and password. Do not use plain FTP on production servers.

Secure Alternatives

  • SFTP (SSH File Transfer Protocol) — Runs over SSH (port 22). Encrypted and authenticated. The recommended replacement for FTP.
  • FTPS (FTP Secure) — FTP with TLS/SSL encryption. Two modes: Explicit (STARTTLS) and Implicit (port 990).

Popular FTP/SFTP Clients

  • FileZilla (free, cross-platform)
  • WinSCP (Windows, SFTP/SCP focus)
  • Cyberduck (macOS/Windows)
Free Tools