The Apple Watch Ultra syncs health, activity and app data with the iPhone, and when it does not, the causes are usually the connection, a paused or limited setting, a full storage or an out-of-date software version, and a short set of checks finds it. First look at the connection. In Control Center on the watch, the connection indicator shows whether it is connected to the iPhone, and on the iPhone, Bluetooth and Wi-Fi must be on and the Watch app open to the My Watch tab, where the status is shown.
The checks in more detail
Keep the watch near the phone and restart both: on the watch, hold the side button and slide the power off slider, and on the iPhone restart normally. The Ultra can also sync over Wi-Fi or cellular when the phone is away, but most data syncs through the phone, so being near it helps. Then the data. In the Health app, check Sharing and the data sources: Settings, Privacy, Health and Apple Watch's access, and that the Activity and Health data are being shared.
In the Watch app, check that the Activity, Workout and Health apps are installed and updated. If workouts do not appear, wait a few minutes after finishing for the watch to send them, and make sure the workout was saved and not discarded. A Low Power Mode on the watch or the phone limits background syncing, so turn it off. If the iPhone is in Low Power Mode, the sync can pause. Software and storage also matter.
Update watchOS and iOS, since sync bugs are fixed in updates, and check that the watch has free storage, in Settings, General, Storage, because a full watch may refuse new data. If syncing still fails after restarts, toggle iCloud Health sync, check that the iCloud account is the same on the watch and phone and that iCloud has space. As a last step, unpairing and pairing again, after making the backup the process offers, rebuilds the connection, but it is long and takes time. Contact Apple Support with the serial number if nothing helps.
Differential
Likely causes of “Apple Watch Ultra will not sync activity or data”, and how to tell them apart
- 1
The watch is not connected
What separates it Control Center shows no connection
How to confirm Reconnect, restart both and keep them close
- 2
Low Power Mode on either device
What separates it Syncing pauses
How to confirm Turn it off
- 3
Health sharing is off
What separates it Workouts or data do not appear
How to confirm Check Health sharing and sources
- 4
A full watch or old software
What separates it Sync fails or stalls
How to confirm Free storage and update
- 5
An iCloud mismatch
What separates it Data does not move between devices
How to confirm Use the same account and check iCloud space
Before you touch a setting
Record this first — changing settings destroys the evidence
- The connection indicator
- Low Power Mode state
- The iCloud account on both
- The software versions
Try in this order
0 of 6 completedCheck the connection
ReversibleIn Control Center.
Restart both devices
ReversibleAnd keep them close.
Turn off Low Power Mode
ReversibleOn both.
Check Health sharing
ReversibleAnd data sources.
Update watchOS and iOS
ReversibleAnd check storage.
Unpair and pair again
ReversibleAs a last resort.
Model-specific
What is true of this model and not of its siblings
- Via the iPhone
- Most data syncs through the phone.
- Low Power Mode
- It pauses background syncing.
Stop boundary
When this stops being a self-service repair
- !If syncing fails after restarts and updates, contact Apple with the serial number
- !Back up before unpairing
- !Check iCloud storage
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Why is my Watch Ultra not syncing?+
The connection, Low Power Mode or a setting.
Does it sync without the phone?+
Partly, over Wi-Fi or cellular.
Do I need iCloud?+
Health sync uses iCloud.
Will unpairing erase the watch?+
Yes, back up first.