Apple Watch Series 12 introduces live heart rate in compact complication

Apple Watch Series 12 and Ultra 4 models now show an actual heart rate reading in the small circular Heart Rate complication — a first for Apple’s wearable interface. This change appears in official marketing material and reflects a hardware-level shift tied to the new Health Sensing System.

How the Heart Rate complication changed

Previously, the small circular version of Apple’s Heart Rate complication served only as a launcher for the Heart Rate app, displaying no biometric data. The wide version, by contrast, showed both a recent reading and a graph of heart rate since midnight. Users who preferred immediate access to metrics — such as resting heart rate trends linked to fitness and stress management — typically selected the wide format.

With Series 12 and Ultra 4, the small complication now displays a live heart rate value. It no longer functions solely as an app icon. That functionality remains unchanged on Apple Watch Series 11 and Ultra 3 running watchOS 27’s release candidate, where the small version continues to act only as a launcher.

What enables the live reading

The upgrade is made possible by the new Health Sensing System, which captures heart rate data every five seconds. That represents a 60-fold increase in sampling frequency compared to earlier Apple Watch models. The higher cadence allows the system to deliver a current, actionable reading even within the space-constrained small complication.

The wide complication retains its dual function: showing the latest reading alongside a time-based visual history. Its additional width accommodates context about when the displayed value was recorded — a detail not conveyed in the compact version.

Pricing and availability

Apple Watch Series 12 is available for pre-order starting at $399. Apple Watch Ultra 4 begins pre-ordering at $799. Both models are scheduled to launch on September 18.