What your watch is measuring
Signals
What your watch records or estimates, with honest limits.
Heart rate variability
Compare intermittent samples with your own baseline.
Learn more →Resting heart rate
Periodic samples, compared with your own baseline.
Learn more →Sleep
A dated estimate of sleep and wake time.
Learn more → Series 8 & later
Wrist temperature
A baseline-relative trend, not a symptom detector.
Learn more →Sleeping respiratory rate
A supporting signal that can strengthen the overnight picture.
Learn more →Your watch records the night. Read it back.
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