SFTP (SSH File Transfer Protocol) is a network protocol that provides secure file transfer capabilities over an encrypted SSH connection. Unlike older protocols like FTP, SFTP encrypts both commands and data in transit, preventing passwords and file contents from being intercepted. It is the most widely used method for secure file transfer in modern IT environments.
How SFTP Works
SFTP operates as a subsystem of the SSH (Secure Shell) protocol. When you connect to an SFTP server, the connection follows these steps:
- SSH handshake — The client and server establish an encrypted SSH connection, negotiating encryption algorithms and verifying the server's identity.
- Authentication — The user authenticates using a password, SSH key, or both. All credentials are transmitted over the encrypted channel.
- SFTP session — Once authenticated, the SFTP subsystem starts. The client can now upload, download, rename, delete, and manage files and directories.
SFTP uses a single connection on port 22 (the standard SSH port) for both commands and data transfer. This is a significant advantage over FTP, which requires multiple ports and creates firewall complications.
Key Benefits of SFTP
Strong Encryption
All data and credentials are encrypted using industry-standard algorithms like AES-256, protecting against eavesdropping and man-in-the-middle attacks.
Key-Based Authentication
SFTP supports SSH key authentication, which is more secure than passwords and enables automated, passwordless file transfers.
Single Port
SFTP uses only port 22, making it firewall-friendly and simpler to configure than FTP or FTPS, which require multiple ports.
Resume and Integrity
SFTP supports resuming interrupted transfers and includes integrity checking to verify that files arrive complete and unmodified.
SFTP vs FTP: What's the Difference?
Despite sharing "FTP" in their names, SFTP and FTP are fundamentally different protocols. FTP (File Transfer Protocol) was designed in 1971 and transmits data — including passwords — in plain text. SFTP was built from the ground up as part of the SSH protocol suite and encrypts everything by default.
For a detailed breakdown of SFTP, FTPS, and FTP, see our SFTP vs FTPS vs FTP comparison.
Common SFTP Use Cases
- Automated backups — Securely transfer database dumps, log files, or application backups to remote storage on a schedule.
- Partner file exchange — Share files with vendors, clients, or partners over a secure channel with access controls.
- Application data feeds — Receive or deliver data files (CSV, XML, EDI) between systems that rely on file-based integration.
- Website deployment — Upload files to web servers securely, replacing insecure FTP-based deployment workflows.
- Compliance requirements — Meet regulatory requirements (HIPAA, PCI-DSS, SOC 2) that mandate encrypted data in transit.
How to Get Started with SFTP
To start using SFTP, you need an SFTP server and a client. You can either set up your own server (using software like OpenSSH or SFTPGo) or use a managed SFTP hosting service like SFTPHub that handles the infrastructure for you.
For step-by-step connection instructions, read our guide on how to connect to an SFTP server.
Key Takeaways
- SFTP is the SSH File Transfer Protocol — a secure, encrypted method for transferring files.
- It uses a single port (22) and encrypts all data and credentials in transit.
- SFTP supports both password and SSH key authentication.
- It is the recommended replacement for FTP in virtually all use cases.
- Managed SFTP hosting services eliminate the need to maintain your own server infrastructure.