The GUI Listen Address

The GUI (and, together with it, the REST API) listens on a single TCP port for HTTP and HTTPS connections. By default this address is 127.0.0.1:8384. The 127.0.0.1 part means “localhost” which means it only listens for connections from the same computer Syncthing is running on. This is a reasonably safe default as it means you need to be logged in on the computer to access the GUI - it cannot be accessed from the network.

To allow access from the network, change the listen address to 0.0.0.0:8384, where “0.0.0.0” means roughly “anywhere”. You should then also set a username and a strong password for authentication and check the option to use HTTPS. You are otherwise, potentially, opening up your Syncthing installation for the world.

Note that specifying your computer’s LAN address (e.g. 192.168.0.123:8384) will NOT restrict access to only devices on your local network! Connections with that address as destination will then be accepted, regardless of their origin. Proper network configuration and security (especially a firewall) is required to enforce such filtering, as it cannot be done reliably by Syncthing itself.

Unix sockets are supported by specifying an absolute path (/run/syncthing/syncthing.socket).

Port Numbers

The default port number is 8384. It’s traditional for custom HTTP services to live somewhere in the 8xxx-series and it’s an unusual enough port that it’s usually free. Syncthing will however choose another, random, port if port 8384 is taken by something else at the time of installation. The port used is always displayed on the console when starting up.

You can change the port number to something else if you prefer, keeping in mind the following restrictions:

  • You can use port numbers in the unprivileged range, 1024 to 65535.

  • The port should not already be used by something else.

Note that changing the port number is a somewhat dangerous operation. If the port number you select is unusable for whatever reason, Syncthing will not be able to present its GUI and you will need to locate and manually edit the configuration file to rectify the situation. Changing the port number on a remote Syncthing installation is not recommended, unless you have other means of access as well.

To use a port number lower than 1024, you will need to:

  • Ensure that Syncthing has the required privilege to open the port. How to accomplish this depends on your operating system - please refer to the relevant operation system documentation. Keep in mind that Syncthing should not, in general, run as a privileged user (root, SYSTEM, etc).

  • Use the advanced config editor or edit the configuration file to set the port number.

We do not recommend using a port number lower than 1024.