What health data does Base read?

Sleep analysis, heart rate variability, resting and walking heart rate, respiratory rate, active and basal energy, steps, bodyweight and workout records including distances. It writes back the bodyweight and nutrition you log, so the platform store stays the single accurate copy.

Does Base work with Garmin, Whoop, Oura or Polar?

Yes, all of them, and without any vendor-specific integration. Each writes to your platform's health store and Base reads from there, which means switching devices does not orphan your data and there is nothing to configure.

Why does the screen show last sync times instead of permissions?

Because iOS deliberately does not tell an app whether read access was denied — a denied type looks identical to a type with no data. Showing a permission checkmark the app cannot actually see would be a fabricated status, so it shows when each type last produced data instead.

Can I revoke access later?

At any time, in your platform's health settings. The features that depend on the revoked type will report no data rather than degrading silently, which is the same rule that governs every missing input in the app.

Health Connections: What Base Reads and Why

Q: Does Base write data back to Apple Health?

With your permission, yes: the bodyweight and the nutrition you log. That keeps the platform store as the single accurate copy rather than creating a second private one that other apps cannot see.

What is read, and what each one does

Data type	Feeds
Sleep analysis	Sleep score, and 20% of recovery score
Heart rate variability (SDNN)	50% of recovery score
Resting heart rate	30% of recovery score, inverted
Walking heart rate average	Submaximal fitness proxy on the heart screen
Respiratory rate	Early illness signal. No score
Active energy	The daily calorie target, as measured
Basal energy	The daily calorie target, projected to 24 h
Steps	Non-exercise movement signal
Bodyweight	Trend weight, and measured maintenance
Workouts and distances	Endurance session matching and grading

What is written back

Bodyweight and the nutrition you log.

Writing back is not a convenience feature. It keeps the platform store as the single accurate copy of your data rather than creating a second private one that no other app can see. If you use another tool that reads nutrition or weight, it should see what you logged here without you entering it twice.

Progress photos are never written anywhere except your own photo library, and never uploaded. The full disclosure.

Why there is no permission checkmark

This is the part that looks like a missing feature and is not.

iOS deliberately does not tell an app whether READ access to a type was denied. This is a privacy design decision on Apple's part and a good one — if apps could detect denial, they could nag, or infer things about you from the pattern of what you withheld.

The consequence is that from inside the app, a type you denied and a type you have no data for are indistinguishable. Both return nothing.

So a green checkmark next to "Sleep" would be a fabricated status. The screen shows when each type last produced data instead, which is the honest signal and is also the one that actually diagnoses a problem: if sleep last synced eleven days ago and you have worn the watch every night, something is wrong regardless of what a permission indicator would have claimed.

Which devices work

All of them, and this is worth being concrete about because it is a common question.

Device	How it reaches Base
Apple Watch	Writes to Apple Health directly
Garmin	Garmin Connect writes to Apple Health / Health Connect
Whoop	Writes HRV, resting HR and sleep to the health store
Oura	Writes to the health store
Polar	Polar Flow writes to the health store
Fitbit	Writes to the health store
Coros	Writes to the health store

There is no vendor preference and nothing to configure. Base has no hardware, no partnership and no integration to break when a vendor changes an API. Switching from a Whoop to an Oura does not orphan your history — both wrote to the same place.

The one thing to check on any of them is that the source app is actually permitted to write to the health store, which is a setting in that app rather than in this one.

When two sources disagree

More than one app can write the same type. Two devices both reporting resting heart rate, or a phone and a watch both counting steps, produce overlapping data.

Base reads from the store and takes the best available value for each day rather than summing sources, because summing two devices that both counted the same walk would double it. Where the platform has already resolved a conflict, Base uses the platform's answer rather than second-guessing it.

The screen also lists apps writing to your health store that Base has no branded row for — a Polar or a Suunto, say — so you can see that the data is arriving even when there is no logo next to it.

Syncing, and why it is not live

Sync runs on app foreground plus a background delivery observer, pulling a window of recent days and writing one summary row per day into the local database.

Two reasons it works this way rather than querying live on every render:

Speed. Reading from the local database is instant and works with the network off. Querying the health bridge on every render would make every screen wait on a native call.

Consistency. A summary row per day means the number on the dashboard and the number in the weekly check-in came from the same read, rather than two reads that happened to land either side of a sync.

Pull to refresh on the dashboard forces a re-sync.

What happens when a type is missing

The feature that depends on it says so.

No sleep data means "no sleep data for last night", not a zero. No HRV for fourteen days means recovery score reports "building baseline" with a countdown, not a number computed from four days. No active energy for the day means the calorie target falls back to committed maintenance plus your surplus, and says that it has.

A wrong number is worse than a missing one. One fabricated zero teaches you that every other number in the app might also be decorative, and that is not recoverable.

What to do next

If a type is not syncing, check the source app's own permission to write to the health store first — that is where it usually breaks, and it is not something this screen can see or fix. What each signal is used for.