OS X Yosemite (version 10.10) is the eleventh release of macOS, shipped on October 16, 2014 — the desktop's iOS 7 moment: the entire interface flattened and translucented in one release, with Helvetica Neue replacing Lucida Grande system-wide and icons redrawn to match the iPhone's new language.

Its functional heart was Continuity: Handoff passing half-written emails between devices, iPhone calls and SMS relayed to the Mac, Instant Hotspot, and AirDrop finally working across Mac and iOS — the ecosystem argument made into features.

The flat redesign with vibrancy blur; Continuity (Handoff, phone relay, SMS, Instant Hotspot); Today widgets in Notification Center; JavaScript for Automation; Spotlight as a centered floating search; iCloud Drive's visible debut; and Mail Drop for large attachments.

Yosemite locked the Mac's visual identity to the iOS era's — every macOS since is a refinement of its look until Big Sur's next reset — and Continuity became Apple's ecosystem moat, the thing rivals with phones but no desktops (or vice versa) could not copy.