watchOS 2 is the second release of watchOS, shipped September 21, 2015. It moved third-party apps onto the watch itself — native code, direct sensor and Digital Crown access — and opened complications to developers, making the watch face the platform's real estate. Time Travel scrubbed complications through time via the Crown; Nightstand mode made the charging watch a bedside clock.

Native apps with ClockKit complications; Time Travel; Nightstand mode; Activation Lock; FaceTime Audio; transit in Maps; and new Photo and Time-Lapse faces.

Native apps and third-party complications defined what a watch platform is; every subsequent watchOS built on this runtime. Speed, however, remained the complaint — solved for good by watchOS 3.