Knowledge Base

How Do You Install an SSL Certificate on a FileZilla Server?

Updated on May 29, 2026

Overview

By the end of this article, a system administrator will have configured a FileZilla Server instance on Windows with an SSL/TLS certificate so that clients can connect using FTPS (File Transfer Protocol over SSL/TLS) instead of plain File Transfer Protocol (FTP). The article covers locating the SSL/TLS settings in the FileZilla Server Options window, pointing the server at the private key file and the certificate file issued in response to the Certificate Signing Request (CSR), saving the configuration, and verifying the first secure client connection. The private key file is the one generated alongside the CSR, and the certificate file is the .pem file received from the Certificate Authority (CA).

What is FileZilla Server?

FileZilla Server is an open-source FTP and FTPS server for Windows. FTPS (File Transfer Protocol over SSL/TLS) wraps the standard File Transfer Protocol (FTP) in an SSL/TLS encrypted channel, so credentials and file transfers are protected in transit. Installing a publicly trusted SSL certificate on the server tells connecting clients that they are talking to the genuine host and lets them establish that encrypted channel without security warnings.

Prerequisites

Gather the following before starting the installation:

A FileZilla Server instance installed on Windows with administrator access to the server console.

The private key file (.key) generated at the time the Certificate Signing Request (CSR) was created.

The issued certificate file from the Certificate Authority (CA) in PEM (.pem) format, containing the server certificate and the intermediate certificate chain.

The on-disk path to both files on the server (for example, C:\Program Files\FileZilla Server\).

Network access on the FTPS listening port from the clients that will connect (default: 990 for implicit FTPS).

Steps

Step 1 — Open FileZilla Server Options

Launch the FileZilla Server administration interface. From the top menu, select Edit and then click Settings to open the FileZilla Server Options window.

FileZilla Server administration menu with the Edit menu openFileZilla Server administration menu with the Edit menu open and Settings highlighted as the option to select.

Image 1 — Edit menu in the FileZilla Server interface with Settings selected.

Step 2 — Enable SSL/TLS support

In the FileZilla Server Options window, select SSL/TLS settings from the left-hand menu. On the right-hand pane, tick Enable FTP over SSL/TLS support (FTPS).

Step 3 — Add the private key file path

In the Private key file box, enter the full path to the .key file generated when the Certificate Signing Request was created. For example: C:\Program Files\FileZilla Server\your_domain_name.key.

Step 4 — Add the certificate file path

In the Certificate file box, enter the full path to the .pem file received from the Certificate Authority. The .pem file must contain both the server certificate and the intermediate certificate. For example: C:\Program Files\FileZilla Server\your_domain_name.pem.

FileZilla Server Options window with the SSL/TLS settings paFileZilla Server Options window with the SSL/TLS settings pane visible. Enable FTP over SSL/TLS support is ticked and the Private key file and Certificate file paths are configured. The implicit FTPS listening port is shown as 990.

Image 2 — SSL/TLS settings pane with the private key file, certificate file, and FTPS listening port configured.

Step 5 — Save the configuration

Click OK to apply the changes. FileZilla Server reloads the SSL/TLS configuration and is now ready to accept FTPS connections.

How to verify success

Open the FileZilla Client on a separate machine and connect to the server over FTPS. On the first secure connection, the client displays the certificate details from the server. Review the common name, issuer, and validity dates, then tick Always trust certificate in future sessions and click OK to complete the connection. A successful login at the FTPS prompt confirms that the certificate is installed and that the encrypted channel is established.

Image 3 — Unknown certificate dialog presented by the FileZilla Client on the first secure connection.

Troubleshooting

Issue: FileZilla Server refuses to start FTPS or rejects the configuration

Cause: The Private key file or Certificate file path is incorrect, or the files are not readable by the FileZilla Server service account.

Solution: Open the SSL/TLS settings pane and confirm that both paths point to the exact files on disk. Use a fully qualified Windows path and check that the FileZilla Server service has read access to the directory.

Issue: Clients see a chain or intermediate certificate error

Cause: The .pem file contains only the server certificate and is missing the intermediate certificate chain issued by the Certificate Authority (CA).

Solution: Rebuild the .pem file so that it includes the server certificate followed by the intermediate certificate(s) from the CA, then update the Certificate file path in FileZilla Server and click OK.

Issue: The certificate does not match the request

Cause: The private key file does not match the Certificate Signing Request (CSR) the certificate was issued for.

Solution: Re-generate the CSR and a matching private key on the FileZilla Server host, request a reissue from the CA, and install the reissued certificate using the matching private key.