Today at its Worldwide Developer Conference, Apple previewed watchOS 2, the first major software update for Apple Watch, giving developers the tools to build apps running natively on the smartwatch.

It allows developers to take advantage of innovative hardware features of Apple Watch including the Digital Crown, Taptic Engine and heart rate sensor, along with software APIs [application programming interfaces] to build new app experiences, says Kevin Lynch, Apple’s vice president of Technology. Available to Apple Watch users this fall, watchOS 2 also includes new watch faces, third-party app information as watch face complications and new communication capabilities in Mail, Friends and Digital Touch.

The new APIs enable audio and video playback and animation, and with the ClockKit framework, developers can represent their data as complications on the watch face. These new tools allow developers to make apps more robust, says Lynch.

For example, Strava can more accurately track your heart rate while on a ride or run using data from the heart rate sensor and accelerometer; Insteon can give customers more precise controls to dim their lights or control the temperature with the Digital Crown; Volkswagen owners can get haptic feedback when their car door has been locked; WeChat includes audio messaging using the microphone; and Vine can host and play video right in the app. 

watchOS 2 lets you turn your favorite photo into a new watch face or view pictures from your favorite photo album with every raise of your wrist with the new Photo and Photo Album watch faces. With the Time-Lapse watch face, you can choose from a selection of time-lapse videos shot over 24 hours in iconic locations including New York City, London or Shanghai.

A new Time Travel feature lets users scroll with the Digital Crown to explore events in the future (and past) including upcoming meetings or activities, the temperature for the week, and information from third-party apps, such as upcoming flight information.

The latest Apple Watch software provides more creative ways to communicate, says Lynch. With Mail, you can respond using dictation, Smart Replies or emoji. You can create multiple Friends screens, each of which can hold up to twelve friends, and new friends can be added directly on Apple Watch. Digital Touch lets you draw and send sketches with multiple colors on the same canvas.

Additional watchOS 2 features include: 

° A Nightstand Mode that transforms the Apple Watch into a bedside alarm clock, with the Digital Crown and side button serving as snooze and off buttons for the alarm;

° The ability to use merchant rewards and store-issued credit and debit cards with Apple Pay, which can be added to Wallet; 

° Support for Transit in Maps, so you can view detailed transportation maps and schedules, including walking directions to the nearest stations with entrances and exits precisely mapped;

° Workouts from third-party fitness apps contributing to your all-day Move and Exercise goals;

° Using Siri to start specific workouts, launch Glances and reply to email;

° Activation Lock, which lets users secure their Apple Watch with their Apple ID, preventing another user from wiping or activating the device if it is lost or stolen.

watchOS 2 will be available this fall as a free update to Apple Watch. Apple Watch requires iPhone 5, iPhone 5c, iPhone 5s, iPhone 6 or iPhone 6 Plus running iOS 8.2 or later. The iOS 9 SDK beta including WatchKit for watchOS 2 is available immediately for iOS Developer Program members at developer.apple.com/watchkit.