Due to limited onboard memory, Fitbit devices only store high resolution (minute or second) data for 5-7 days, depending on the device model. If a device has not synced for more than 5 days, the device will start to remove the oldest high resolution data and store only daily aggregate values.

Additionally, if the device is in low power mode (has a very low battery) then the high resolution data may be unreliable. In this instance, it is best use the daily aggregate values as they will reflect more accurate information about activity.

In order to guarantee that the highest resolution data is available for your project we recommend informing participants to sync their device at least once every 5 days (or more frequently if possible), and charge the device as soon as they receive a low battery notification.

You can always check on battery life and device sync behavior from your project dashboard. For more details on device compliance visit our device compliance information article