The most major update is to the dashboard, where you'll now see more details about your exercise and sleep. You just have to swipe up from the bottom and you'll get to see data from up to seven metrics of your choosing. You can choose between core stats, hourly steps, heart rate, exercise, water, food, weight and badges.
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You'll also now be able to log your water intake and weight on the watch itself, something that could previously only be done in the phone app. You can do that within the Today dashboard, just click the little "+" button and you'll be prompted to add your water or weight. There's also the ability to set goal-based exercises - in either distance, time or calories - for more than 15 activities. You'll also be able to see all that real-time progress on your wrist.
Fitbit also announced it's rolling out 10 new partner apps and clock faces, four of which are available now: MySwimPro, Couch to 5K, Genius Wrist (which provides on-device workouts) and achu health (a clock fact that gives you alerts if your body is showing signs of sickness). The other six - Charity Miles, FitBark, Gold's Amp for Fitbit, Mindbody, Noonlight, TRX - will arrive early 2019.
Also coming early next year are period trends for Fitbit's Female Health Tracking, letting you view your menstrual cycle data, logged symptoms and trends in the app.
If you hold the left button, you'll also be able to quickly access Fitbit Pay, music controls and quick settings for screen wake and notifications. Speaking of new settings, you can also keep the clock screen on for up to 60 seconds.
Finally, Fitbit is rolling out a new Exercise API and open-source tools that should make it easier for developers to create apps for more complex activities like skiing and snowboarding - so ones that don't focus on steps.
The 3.0 update will be rolling out over the course of this week, so don't worry if you don't yet see it.