Sleep score in Fitbit
Fitbit comes with improvements for your sleep stats. Where before you mainly saw one overall figure, now you get more insight into what's behind it. The revamped score shows which components influence your sleep. Think about how long you sleep, how fast you fall asleep and how often you wake up at night. Those extra details help you better understand why you feel fitter some days than others.

The update revolves around six key metrics. For instance, total sleep duration remains a big factor, but it also looks at how quickly your body actually rests. Deep sleep, restlessness and interruptions also play a role. The number of times you were actually awake also counts. Together, that data gives a more complete picture of your night.
According to Google, which is behind Fitbit, this approach should help not only measure your sleep, but also better understand your habits. So you will not only see what is happening, but also where you can possibly improve.
If you use Fitbit Premium, you'll get additional guidance on top of that. For example, the app can give targeted tips if you have trouble falling asleep, such as stopping using screens earlier or trying relaxation exercises. You can also get explanations for fluctuations in your score, such as after a busy day or an afternoon nap.
Initially, the new view is being rolled out via a test version, so you may not see it on your device just yet.