Windows: Settings > System > About > Processor
Windows: Task Manager > Performance > CPU
Windows: System Information > Processor
Mac: Apple menu > About This Mac > Chip or Processor
Linux: Open Terminal and run `lscpu`
Linux: Open Terminal and run `cat /proc/cpuinfo`
Chromebook: Settings > About ChromeOS > Diagnostics
iPhone/iPad: Settings > General > About
Android: Settings > About phone > Processor or Hardware information
Check the device manual or manufacturer support page
Check the original product listing or receipt
Use a system info app or tool if needed