Apple’s latest wearable lineup—Series 12 and Ultra 4—is introducing a subtle yet meaningful change in its heart rate complication that many users will appreciate. The new Health Sensing System onboard these models enables readings every five seconds, about 60 times more frequently than in prior versions. That uptick in precision unlocks the possibility of displaying live heart rate data, even in the smaller complication formats. Previously, only wider complication styles could show recent heart rate readings and trends; the tiny circular version merely served as an app launcher. With Series 12 and Ultra 4, even the compact complication can now show your current heart rate in real time.
Why the complication update matters
Up until now, Apple Watch users who chose the small heart rate complication saw very limited functionality. That version just launched the Heart Rate app—it offered no glanceable data. If you wanted to see your heart rate at a glance, you had to pick the wider format, which takes up more screen space but also displays a graph of your heart rate since midnight alongside the latest reading.
With the five-second sampling power of the new Health Sensing System, Series 12 and Ultra 4 can continuously measure your heart rate and provide live updates. It’s this higher refresh rate that makes it feasible for even small complications to show data instead of acting only as an icon. Starting with watchOS 27, Series 11 and Ultra 3 devices still use the app-launcher version in small complication spots. So this upgrade marks the first time all complication sizes can convey live heart rate on newer hardware.
When you’ll get it & what it costs
The new complication behavior is already on display in Apple’s promotional materials for Series 12 and Ultra 4. These watches are available for preorder, with Series 12 starting at $399 and Ultra 4 at $799. Both models are slated to ship on September 18. At that point, the enhanced heart rate complication will be available out of the box for those models. For existing owners of Series 11 and Ultra 3, the small heart rate complication will remain limited to its launcher style since the hardware doesn’t support the new rapid-sampling sensor.
Incremental changes like this might seem modest but they add significantly to the user experience. Live visual feedback from health sensors deepens interaction without requiring you to dig into apps—something many wearers find valuable.
