What is SFTP?
A practical explanation of SFTP, FTP and secure file exchange between systems and people.
SFTP stands for SSH File Transfer Protocol. The protocol is used to upload, download and manage files over an encrypted SSH connection. It is widely used in businesses, automated integrations and systems where files need to move without exposing credentials and contents over the internet.
How does SFTP work?
An SFTP client connects to an SFTP server using a hostname, port and username. The server identifies itself with a host key, while the user normally authenticates with a password or SSH key. Once connected, the client can work with the folders and files the user is authorised to access.
SFTP typically uses TCP port 22 and runs over SSH. This protects credentials, commands and file contents in transit. An encrypted connection does not automatically protect a file before upload or after download, and it does not replace backups.
SFTP, FTP and FTPS are not the same
| Protocol | Transport protection | Typical port | Practical difference |
|---|---|---|---|
| FTP | No encryption by default | 21 plus separate data connections | A legacy solution that should generally not be used over the internet without additional protection. |
| FTPS | FTP protected by TLS | 21 or 990 plus data connections | Retains the FTP model but adds TLS. Firewall configuration can be more involved. |
| SFTP | Encrypted through SSH | 22 | A separate protocol with one encrypted connection and broad support in integration tools. |
When does an SFTP server make sense?
SFTP is well suited to predictable file exchange when email or manual sharing links do not fit the workflow. Typical examples include:
- An ERP or accounting system delivers CSV files to a business partner.
- An online shop exports orders, product data or images to another system.
- A script uploads reports or backup files to a temporary recipient.
- A supplier needs access to one restricted folder without seeing other customers' files.
- A recipient needs to download a file in a web client while the sender's system continues uploading through SFTP.
How to assess security
SFTP is a strong starting point, but overall security depends on the surrounding setup. Use this short checklist:
- Verify the server's host key. The fingerprint helps the client detect a connection to an unexpected server.
- Use unique credentials. Do not reuse passwords across systems or recipients, and rotate them when needed.
- Restrict access. Each integration should only access the folder and quota it actually needs.
- Delete files after transfer. A transit solution should not become a permanent, uncontrolled archive.
- Keep the original and a backup. A file server or transfer service must not be the only copy of important data.
- Assess how sensitive the data is. Encrypted transport is only one security layer. Highly sensitive files may require additional encryption, agreements and documented controls.
Where does SikkerFTP.dk fit in?
SikkerFTP.dk provides a ready-to-use, isolated SFTP endpoint without requiring you to install and operate an internet-facing server. Each endpoint has its own technical user, folder and quota. Administration and file transfer are brought together under SikkerFTP.dk, while endpoints remain compatible with standard SFTP clients and integrations.
The free beta is deliberately limited to data in transit. Files are stored on self-hosted equipment in Denmark and protected by SFTP or HTTPS in transit. Customer files are not backed up or encrypted on the data disk yet. The sender must therefore always retain the original, and high-risk data must not be used in the beta.