Pfsense Serial Number ((better))
When managing a pfSense firewall, the "serial number" can refer to two different things: the (relevant for appliances like Netgate SG-1100, SG-3100, etc.) or the software license serial number (relevant for pfSense Plus).
The easiest way to find the serial number on any running pfSense instance is via the dashboard: Log in to the pfSense WebGUI Look at the System Information widget on the main dashboard. Netgate Device ID pfsense serial number
Or check via:
From the Shell (Option 8):