Select to Copy watches for text selections and pushes them to the clipboard, and (when clipboard sharing is on) to your other Macs, without pressing ⌘C.
Enable
Settings → Advanced → Select to copy (on by default).
Works alongside Clipboard sharing. Selections respect the same size cap and direction settings as manual copies. Select to Copy is a Pro feature; see Free vs Pro.
Detection mode
Precise copies only clear text selections and never beeps. Balanced also catches drag or double-click selections in apps that hide their selection state; start here. Eager is the most aggressive and may over-copy or occasionally beep in difficult apps. Switch to Precise if copies fire too often.
Copied flash
Turn on Show copied flash for a brief on-screen Copied confirmation after an auto-copy (off by default).
Privacy
Concealed clipboard items, passwords and other secret pasteboard types, are never copied or sent. See Settings → Privacy & Security.