On Windows, press Ctrl + Shift + Esc, open Task Manager, and check the Performance tab under Memory
On Windows, press Windows + Pause/Break and look for Installed RAM
On Mac, click the Apple menu, choose About This Mac, and check Memory
On Linux, open a terminal and run free -h
On Linux, open a terminal and run cat /proc/meminfo
On Android, go to Settings, then About phone, and look for RAM or Memory
On iPhone, go to Settings, then General, then About, and check available device information
On Chromebook, open Settings, then About ChromeOS, then Additional details, and check Memory
On a desktop or laptop, check the system specifications label or manufacturer page for the model
On BIOS or UEFI, open the firmware settings and look for installed memory information