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Clarify interval sync behavior for offline devices
If using interval syncs, what if my phone has been without connection to the watch for longer than the interval? Will there be missing data that is then not synced to my local device?
MC NaveenPinnedJul 14, 2026
Great question — short answer: missing an interval while the watch is disconnected usually does not permanently drop data.
How interval sync works:
- It does not only pull “the last N minutes since the previous run.”
- Each background/manual sync reads Health Connect over a rolling 48-hour window, then sends only records newer than the per-type last-successful-sync watermark.
- That watermark advances only when records for that type are successfully delivered. Empty “no new data” runs do not push it forward.
So if the phone and watch are disconnected longer than your interval:
1. During the gap, Health Connect on the phone simply will not have that watch data yet, so syncs may find nothing new for those types.
2. When the watch reconnects and writes/backfills into Health Connect, the next interval (or Sync Now) will pick those records up — as long as they still fall inside the 48-hour lookback and are at/after the watermark for that type.
Caveats:
- Hard limit: default sync only looks back 48 hours. If the device was out of contact longer than that, older points may not be included unless you do an explicit longer-range read (for example local HTTP GET /?days=N, which is a full-window read without watermarks).
- Edge case: if another source already advanced a type's watermark past a gap (e.g. phone steps while the watch was offline), late watch backfill with older timestamps can be skipped by incremental filtering. In that situation, use Sync Now after reconnect or an explicit range read.