Stats

free, open-source macOS system monitor that lives in the menu bar. shows CPU, RAM, disk, network, battery, and more at a glance.

installed via: brew install --cask stats

why over iStat Menus: free, actively maintained, and does what you need without the subscription.

menu bar neighbor: sits alongside Bleed, f.lux, Amphetamine, Backtrack, and Time Machine — all managed by Ice so they don't clutter the bar.