The retina display is over 30 percent larger than Series 3, so you can see more information at a glance.

Performance

• S5 System in Package is up to two times faster than Apple Watch Series 3, so apps are faster and launch quicker
• Speaker is 50 percent louder than Apple Watch Series 3, so calls, using Siri, and other voice interactions are even better
• All-day battery life, up to 18 hours

Compass and always-on altimeter

• Built-in compass shows your direction, incline, and latitude and longitude, even without a Wi-Fi or cellular connection
• See your real-time elevation change foot by foot with the always-on altimeter and still enjoy all-day battery life
• See your direction, location, and elevation change at a glance with watch face complications 

Heart Health

• Apple Watch can check your heart rhythm in the background and alert you to an irregular rhythm that appears to be atrial fibrillation (AFib)
• With the optical heart sensor, you can check your heart rate at any time in the Heart Rate app—and see your resting, walking, and workout recovery heart rates
• Heart rate notifications tell you if your heart rate is above or below a certain number of beats per minute

Swim proof

• Swim proof with a water resistance 50 meter rating, so you can take can take Apple Watch SE to the pool, ocean, and shower

Workouts

• With watchOS 8, Apple Watch SE can detect when you’re riding a bike and remind you to start a workout—and can automatically pause and resume when you stop temporarily
• The Outdoor Cycling workout algorithm more accurately calculates calories when you’re riding a pedal-assisted e-bike
• Use Voice Feedback to hear metrics like pace, speed, progress toward Activity rings and goals, and more
• Fall detection is optimized for workouts (coming later this year) and can detect a hard fall, initiate a call to emergency services, and alert your emergency contacts

Music, Podcasts, and audiobooks

• Stream Apple Music, Apple Podcasts, or audiobooks from Apple Books right on your watch, or sync content from iPhone