When starting up your UniFi controller on your server, you might be prompted with the error saying “Start-up failed” as the screenshot below.

Some might manage to see that the application says that Port 8443 is in use by another application. Some CCTV applications or other web applications installed on the server would use the same port.

Here you would have two choices, you can uninstall the conflicting application or just change the port of the UniFi controller.

To change the port of the UniFi controller, you need to open the system.properties file from C:\Users\<user name>\Ubiquiti UniFi\data.

Remove the hash from the below lines and change the port to 8445 and both lines should be as below.

unifi.https.port=8445
portal.https.port=8445

Save the file and close Notepad. Open the UniFi Controller and the issue will be resolved and the service will start with no issues.