The heart rate monitoring on the Apple Watch SE (2nd Gen) is generally pretty reliable, according to our research. It's equipped with an optical heart rate sensor that checks your heart rate during workouts, when you're resting, and throughout the day.
Our data shows that it's quite accurate for steady activities like running, walking, or using an elliptical. But, like many wrist-worn heart rate monitors, it might not be as precise during exercises with quick wrist movements, like high-intensity interval training (HIIT). That's not unusual for these types of sensors and isn't something specific to the Apple Watch.
The watch can also track your resting heart rate, which is great if you're keeping an eye on your cardiovascular fitness over time. Lots of people find this feature super helpful when combined with other health features on the watch.
Plus, the built-in Health app can give you alerts if your heart rate goes too high or too low, and you can set these to suit what you need. This can be especially useful if you're paying close attention to your heart health.
From what we've gathered, while the Apple Watch SE (2nd Gen) isn't as accurate as medical-grade devices, it does a solid job for most everyday fitness activities.
If you're thinking about getting it mostly for heart rate tracking, it might be a good idea to try it out and see if it works well for your specific needs—and don't forget, pairing it with an iPhone gives you even more detailed info in the Health app.