Sleep Tracking API: How to Get Sleep Data Into Your App
Updated July 24, 2026
Sleep tracking is really two different things behind one word. Sleep duration and time in bed are measured reasonably well from a device worn overnight, but sleep stages (light, deep, REM, awake) are estimated — modeled from movement, heart rate, HRV, and respiration, not read from EEG. Worse for anyone merging sources: vendors label and split those stages differently, so two APIs can describe the same night with different words. The data comes from wrist wearables and rings worn to bed (Oura, WHOOP, Fitbit, Garmin, Apple Watch) via the on-device stores (HKCategoryTypeIdentifierSleepAnalysis, SleepSessionRecord) or cloud OAuth APIs. Best pick: Oura or WHOOP for a rich stage-plus-readiness bundle; an aggregator if you need to reconcile several brands. If you want the physiology of the stages themselves, see what are sleep stages — this page is about getting the data.
Where you can get sleep data
Sleep needs a device worn overnight. Phones alone typically do not produce reliable staged sleep — treat phone-only "sleep" as coarse, and confirm which device actually generated the record. Field names, scopes, and stage enums change often; treat everything below as "as of 2026, verify" against each provider's live data dictionary.
| Source | How you access it | Notes |
|---|---|---|
| Apple HealthKit (iOS) | On-device read, per-type permission | HKCategoryTypeIdentifierSleepAnalysis with HKCategoryValueSleepAnalysis values (inBed, awake, asleepUnspecified, and stage-specific asleepCore / asleepDeep / asleepREM on supporting OS versions). No cloud pull — read in-app. Best with an Apple Watch worn to bed. |
| Android Health Connect | On-device read, per-record permission | SleepSessionRecord — a session with start/end and stages (deep, light, REM, awake). On-device datastore other apps write into; no cloud endpoint. |
| Oura API v2 | Cloud OAuth 2.0 | /v2/usercollection/sleep for detailed per-period data including stages and latency, plus daily_sleep score and sleep_time. Data appears only after an app sync. |
| WHOOP API v2 | Cloud OAuth 2.0 | Sleep data with Light, REM, and Slow-Wave (Deep) via v2/cycle/{cycleId}/sleep. Verify current endpoint and stage fields. |
| Fitbit Web API | Cloud OAuth 2.0 | Sleep endpoints returning stages (durations in seconds) and sleep type. |
| Garmin Health API | Cloud OAuth 2.0 | Sleep summaries including sleep stages; coverage is device-dependent. |
| Aggregators (Terra, Junction, Rook) | One cloud OAuth + normalized schema | Normalize sleep sessions and stages across providers — useful precisely because vendor stage schemas differ. See wearable data APIs. |
Note that Strava exposes no sleep data — it is an activity platform only.
Measured or estimated?
Be honest about which half you are working with:
- Duration and time in bed: measured reasonably well from an overnight-worn device. This is the reliable part.
- Sleep stages: estimated / modeled from motion (actigraphy) plus heart rate, HRV, and respiration — not EEG. They are validated against clinical polysomnography only imperfectly. Do not present consumer sleep stages as clinical-grade, and do not use them to diagnose sleep apnea or any sleep disorder. This is a wellness signal, not a diagnostic.
The headline gotcha for developers is stage-mapping. Vendors do not agree on a taxonomy: Apple uses Core / Deep / REM / Awake; others use Light / Deep / REM; WHOOP uses Light / REM / Slow-Wave (Deep). Definitions of "in bed" versus "asleep," plus sleep-onset and wake detection, also vary. When you merge sources you must map stages explicitly — you cannot assume a 1:1 equivalence, and you should not claim cross-vendor comparability without documenting that mapping. Do not publish accuracy percentages; none is sourced here, and they vary by device and person. Verify each provider's exact stage enum and field names before shipping any merge logic.
One more timing note: cloud data is latent. Sleep and readiness values land only after the user opens the vendor app or the device syncs, so this route is not suited to hard real-time.
Which should you pick?
- Richest stages plus a readiness or recovery bundle: Oura or WHOOP, where nightly staging feeds a score out of the box. Compare the two in Oura vs WHOOP.
- iOS-native sleep with staging: HealthKit
HKCategoryTypeIdentifierSleepAnalysis, with an Apple Watch worn to bed. On-device keeps the data on the user's phone until you choose to upload it. - Android, on-device: Health Connect
SleepSessionRecord, inheriting whatever a paired wearable wrote. - Several brands at once: an aggregator so you get one normalized schema and can reconcile the differing stage taxonomies in one place instead of N.
Before you ship
Re-verify each provider's current stage enum, field names, and OAuth scopes against its live data dictionary — these change often. Keep the framing honest with your users: duration is measured, stages are an estimate, and consumer sleep data is a general wellness signal, not a medical diagnostic. If you are combining sources, write down your stage-mapping and surface which device produced each night's record.
Frequently asked questions
- Are sleep stages from a wearable accurate?
- Sleep stages (light, deep, REM, awake) are estimated from movement, heart rate, HRV, and respiration, not from EEG, so they are modeled rather than measured. Duration and time in bed are more reliable. Consumer stages are a wellness signal, not a clinical or diagnostic tool, and accuracy varies by device and person. Verify each provider's method in its data dictionary.
- Can I get sleep data from a phone without a wearable?
- Typically not reliably. Phones alone usually do not produce trustworthy staged sleep, so phone-only sleep should be treated as coarse. Reliable sleep data comes from a wrist wearable or ring worn overnight, such as Oura, WHOOP, Fitbit, Garmin, or Apple Watch. Confirm which device generated any record before using it.
- Why do sleep stages differ between Oura, WHOOP, and Apple?
- Vendors use different stage taxonomies. Apple uses Core, Deep, REM, and Awake; others use Light, Deep, REM; WHOOP uses Light, REM, and Slow-Wave (Deep). Definitions of in-bed versus asleep also vary. If you merge sources you must map stages explicitly and cannot assume a 1:1 match. Verify each provider's stage enum before combining data.
- How do I access sleep data on iOS and Android?
- On iOS, read HealthKit's HKCategoryTypeIdentifierSleepAnalysis on-device with the user's permission. On Android, read Health Connect's SleepSessionRecord, also on-device. Neither is a cloud API. For server-side access across users, use cloud OAuth wearable APIs (Oura, WHOOP, Fitbit, Garmin) or an aggregator. Verify current field names and scopes.
- Can sleep tracking APIs diagnose sleep disorders?
- No. Consumer sleep data is a general wellness signal, not a medical diagnostic. Stages are estimates validated only imperfectly against clinical polysomnography, so they should not be used to diagnose sleep apnea or other disorders. Frame the data as wellness insight and direct users to a clinician for any medical concern.
Keep reading
Independent comparison, last reviewed July 24, 2026. Pricing, rate limits, and feature availability change often — confirm current details in each provider’s official documentation before you commit. Product and company names are trademarks of their respective owners; AIFitnessAPI is not affiliated with, endorsed by, or sponsored by any product listed here.
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