On Windows, open Settings > System > About and look for Device name
On Windows, press Windows key + Pause/Break and look for Computer name
On Windows, open Command Prompt and type hostname
On Windows, open Command Prompt and type systeminfo and find Host Name
On Mac, open System Settings > General > About and look for Name
On Mac, open Terminal and type scutil –get ComputerName
On Linux, open Terminal and type hostname
On Linux, open Terminal and type hostnamectl
On ChromeOS, open Settings and look for Device name