Early Signal and Apple’s Vitals app
Both read overnight Watch metrics against your own range. They are different products with different jobs.
Last reviewed 2026-09-24 · Sources · Editorial policy
01What Vitals is for
Vitals ships with Apple Watch. After you wear it to sleep—Apple says about seven nights to establish a typical range—it classifies overnight metrics as typical or outside that range. A notification can fire when multiple metrics are out of range, with context about factors that may be involved. Wrist temperature needs Series 8 or later, or any Ultra.
02What Early Signal adds on top of Health
Early Signal does not replace the Watch. It reads samples already in Apple Health and scores them on your iPhone. Wrist temperature and breathing lead when present. HRV and resting heart rate support. Sleep is context. The status ladder is Typical, Slightly off, or Off from usual, and Off from usual pushes are capped. Apple’s published Vitals metric list does not include HRV; Early Signal uses HRV from Health as its own supporting signal.
03Where the data stays
Vitals is Apple’s app on the Watch. Early Signal’s scoring stays on the iPhone. Neither comparison here is a claim about clinical accuracy. If you feel unwell, seek care regardless of either screen.
| Early Signal | Apple Vitals | |
|---|---|---|
| Hardware | iPhone app that reads the Apple Watch you already wear. | Built into Apple Watch. |
| Signals | Wrist temperature and breathing lead when present. HRV and resting heart rate support. Sleep is context. | Overnight heart rate, respiratory rate, wrist temperature (Series 8 and Ultra), blood oxygen where available, and sleep duration. HRV is not in Apple’s published Vitals list. |
| Where it runs | Scoring stays on the iPhone, using samples already in Apple Health. | Apple’s app on the Watch, after about seven nights to learn a typical range. |
| Status | Typical, Slightly off, or Off from usual. Off from usual pushes are capped. | Overnight metrics are typical or outside your range. A notification can fire when multiple metrics are out of range. |
| Limits | Wellness tool. Does not diagnose or treat disease, and is not medical advice. | Not a medical device. This page does not rank the products. |
Guide FAQ
01Is Early Signal a replacement for Vitals?
02Does this page rate Apple?
Sources
Public documentation cited as context—not as clinical validation of Early Signal.
How it compares
Related guides
Apple’s Vitals app, explained
What the built-in Vitals app shows overnight, and how that differs from Early Signal.
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Can Apple Watch show you need a rest day early?
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How accurate is Apple Watch wrist temperature?
Sleeping wrist temperature is a personal trend, not a clinical thermometer.
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