Set it up once. It syncs itself.
Auto Sync is an iPhone app that copies the measurements from your Fitbit account into Apple Health, automatically. It reads your weight, body fat, and sleep — including the light, deep, REM and awake stages — and saves them into the Health app a few times a day in the background, so you never have to open anything or press a button.
You sign in once with the Google account your Fitbit belongs to. There is no Auto Sync account to create and no server of ours in the middle: the data goes from Google's Fitbit API straight into Apple Health on your own iPhone.
Step on the scale and the number lands in Apple Health on its own — no buttons, nothing to remember. Opening the app syncs on the spot.
Light, deep, REM, awake — the whole night as Fitbit scored it, not just a total.
The first sync imports everything your Fitbit account holds — years of weigh-ins and nights. After that it just keeps up.
Your data goes from Google's Fitbit API straight into Apple Health, on your phone. There's nowhere else it could go.
Works with any Fitbit tracker or Aria scale. Fitbit data is served by the Google Health API. Auto Sync is an independent app, not affiliated with or endorsed by Google, Fitbit, or Apple.