What is the difference between the two apps?
Sync Solver - Fitbit to Health (the red icon, listed in the App Store as Sync Solver for Fitbit) allows you to sync data from your Fitbit account into Apple's Health app. For example, if you have a Fitbit Flex you can send step counts into Health, or if you have a Fitbit Aria scale you can send weight measurements into Health.

Sync Solver - Health to Fitbit (the green icon) allows you to sync data from Apple's Health app into your Fitbit account. For example, if you have an Apple Watch you can send heart rate values into your Fitbit account, or if you track steps with a Misfit you can send steps into your Fitbit account. Read More

Note: For any given data type, you should only sync it in one or the other app, not both. For example, if you have a Withings scale and send weight measurements to Fitbit using Sync Solver - Health to Fitbit, you should not sync weight to Health using Sync Solver - Fitbit to Health, since the weights will already be in Health causing duplicates.
Why does it need read access to the data in Health?
As the app syncs throughout the day, it must compare each new data point with the data points that have already been downloaded. If the app does not have read access, it will not be able to compare the data points, and you may end up with duplicate data in Health. If you have already performed several syncs without giving the app read access, you may need to delete the app, including all Health data, and reinstall.
Does it sync heart rate?
Heart Rate is not supported because it requires Partner API access. The current version of Sync Solver requests access to your Heart Rate data in anticipation of adding this feature in a later version. See Why does it only show one data point per day? for more details on our Partner API application.
Why does it say "Unable to finish sync, Fitbit Unavailable (403)
It is possible that your Fitbit login needs to be refreshed. Open this link to force a logout, and then reinstall Sync Solver to correct the issue.
Why does it say "Unable to finish sync, Fitbit Unavailable (500)" or "Unable to finish sync, Check your network connection"?
Fitbit currently has a bug with active calories which can cause this error message to appear. Click here to learn more
Why does it say "Unable to finish sync, Health unavailable"?
There appears to be a performance issue with Apple Health on older phones and/or when syncing with a Fitbit account with many years of data. In most cases this issue can be corrected by performing a hard restart on the phone (hold the home and power button at the same time). If the issue persists, please file a bug report with Apple so that they will prioritize correcting this issue.
Is there a way to avoid double counting steps, distance, etc?
Yes. If you still want to track the iPhone's steps in Health but just avoid double counting, open the Health app and navigate to Health Data > Activity > Steps > Data Sources & Access. Next, tap Edit in the top right corner and drag Sync Solver to the top of the list of Data Sources. This will make Sync Solver the highest priority Data Source in Health, which will instruct Health to use data from Sync Solver instead of the built-in sensor on the iPhone when the date periods do not overlap. If you no longer want to track data from the iPhone at all, open the iOS Settings app, and navigate to Privacy > Motion & Fitness and turn the Fitness Tracking switch off.
How often does it automatically sync?
By default, the app is set to use the Balanced Background Update Strategy setting. In the best case scenario, this would result in automatic syncing every hour. In real world conditions, it generally results in 2-4 syncs per day. To change the Background Update Strategy, open the iOS Settings app, navigate to Sync Solver > Background Update Strategy, and select either Aggressive or Battery Saver. Aggressive typically results in 4-6 syncs per day, and Battery Saver typically results in 1-2 syncs per day. If you want to know when it automatically syncs without opening the app, open the iOS Settings app, navigate to Sync Solver > Show New Data Badge (or Notification) and turn the switch on.
Note: If you upgraded from version 1.0, it may take some time for iOS to learn the new background update pattern. Reinstalling the app can speed this process up.
Why is it not automatically syncing?
In order for the app to automatically sync, your device must be on, unlocked and connected to the internet. Apple considers Health data protected (Learn More) and does not allow Sync Solver access when your device is locked. If you want the app to sync more frequently, open the iOS Settings app, navigate to Sync Solver > Background Update Strategy and choose Aggressive.
Note: Sync Solver uses an iOS feature called Background App Refresh to enable automatic syncing. Since iOS schedules backgroud updates based on your app usage pattern, it may be necessary to manually sync from time to time in order to establish a more consistent Background App Refresh pattern for iOS.
Why does it keep asking me to login to Fitbit?
Fitbit only allows Sync Solver to save your credentials for up to 30 days. You will need to login again when the credentials expire.
Why does it not let me login to Fitbit?
If the browser redirects me back to the login page with no error message when attempting to login to Fitbit, it probably means that you have cookies disabled in Safari. Fitbit requires that you enable cookies in order to login to their website. Open the iOS Settings app, navigate to Safari > Block Cookies and choose one of the Allow options.
Why is the latest data from my Fitbit device not available yet?
Your Fitbit device must be within range of the receiver to send data. If you use the Fitbit app on your iPhone, make sure to enable All-Day Sync to achieve the best results.
Why does it sync incorrect data from my Fitbit account?
The latest version of Sync Solver uses the new Fitbit API, which uses a Safari popup window to validate your credentials. If you previously logged in to Fitbit with a different account in Safari on your phone, it is possible that this login has been remembered, and you are connected to the wrong account. Open this link to force a logout, and then reinstall Sync Solver to correct the issue.
Why is my data not on the Health Dashboard?
The Health app does not show any data types on the Dashboard by default. Instead, Health requires you to manually select each data type that you want on the Dashboard. For example, to add Steps to the Dashboard, navigate to Health Data > Fitness > Steps > Show on Dashboard and turn the switch on.
Why can't I find Sync Solver in the App Store?
Sync Solver only works on devices that have the Health app. Currently, that includes iPhones and iPod Touches running iOS 8.1 or later. You will not be able to find Sync Solver in the App Store while using an iPad.
Is there a way to change which data types it syncs after the initial set up?
Yes. Open the Health app and navigate to Sources > Sync Solver.
Why does it only show one data point per day?
The standard Fitbit API only supports data granularity at the daily level. We have applied for Partner API access to provide intraday data (including Heart Rate), but Fitbit has not been approved our application.
Does it sync historical data?
The app will sync all previously recorded data, and then it will sync the latest data on an ongoing basis.
Why are there historical data points for days before I started using Fitbit?
The Fitbit API allows apps to download historical data for a specific range of dates or all data up to the current day, but it does not not provide a way to determine when a user first started recording data. Because of this, during the first sync, Sync Solver requests all historical data for each type that you enabled at the Health access prompt. Our testing shows that when the Fitbit API fulfills this request, it arbitrarily uses a range of dates including today through three years ago. If you don't have data going back for that amount of time, it will return interpolated data for the period between three years ago and when you started recording data for certain data types, such as body measurements. See Why do some data points show the same value, or averaged values, multiple days in a row? for more details on interpolation, and why it is a difficult issue to correct.
Why do some data points show the same value, or averaged values, multiple days in a row?
When downloading body measurements such as weight, the Fitbit API interpolates gaps in your data. If you do not have any measurements for the current day, Fitbit with use the previous day’s value. If you have a period of days where there are two measurements at either end, Fitbit will compute an average of the values resulting in a linear increase or decrease over the period. Unfortunately, this behavior is not something that we have control over, and there is no way for the app to know when the Fitbit API is returning an interpolated value versus a measured value.

Example 1: If you take a 70kg weight measurement on September 5, and today is September 8, Fitbit will report all the days between the two dates (Sep 6, 7, 8) as 70kg.
Example 2: If you take a 70kg weight measurement on September 5, and another measurement of 75kg on September 7, Fitbit will report 70kg on Sep 5, 72.5kg on Sep 6, and 75kg on Sep 7.
Why is it unable to complete the sync on active calories?
There is an issue with the Fitbit API at this time. We have a support request in to Fitbit asking them to resolve it, and this is their current response:

Thank you for reporting the issue. I have forwarded this issue to the appropriate Fitbit engineering team. While we will address the issue, this is not a common use case and other issues currently have much higher prioritization.

In the meantime, we have found that if you manually sync a few times in a row, it will usually download Active Calories eventually. After it syncs the Active Calories once, future syncs will be much faster. If it still does not work even after several attempts, we recommend disabling Active Calories until Fitbit resolves the issue. Click here to learn how to disable data types after the initial setup
Why do the calories not match?
The discrepancy is one of labelling.

Health has categories for Active and Resting Calories but not Total Calories (what Fitbit calls Calories Burned). What Apple means by Active Calories is only those calories "burned due to physical activity and exercise” (see HKQuantityTypeIdentifierActiveEnergyBurned in the Apple developer reference).

Fitbit does have a value for what Health calls Active Calories - they call it Activity Calories (see activities/activityCalories under the Calorie Time Series Differencess section in the Fitbit developer reference). Even though the Fitbit API allows you to get data with this level of specificity, the Fitbit dashboard does not show these numbers. Rather, the Fitbit dashboard only allows you to view the Calories Burned number, which does not equal the Calories BMR (what Health calls Resting Calories) or Activity Calories (what Health calls Active Calories). Furthermore, due to the way Fitbit calculates Activity Calories and Calories BMR, their Calories Burned number does not equal the sum total of the two.
Why does the sleep analysis not match?
Health talks about sleep in terms of a start/end time In-Bed and a start/end time Asleep. The start/end time Asleep should always be a subset of In-Bed (how can you be asleep if you’re not in bed?).

Fitbit also talks about things in terms of start/end time In-Bed, but their Asleep category is slightly different. While Fitbit does record the start time of your sleep, they also record how many times you wake up and for how long you are awake each of those times. Fitbit also records the final time you wake up, and then reports your Total Sleep Time as the duration between when you first went to sleep and the last time you woke up, less the number of minutes you were awake throughout the night.

This means that, in order to convert Fitbit’s numbers into Health’s Asleep category, we had to make a trade-off and choose between two different approaches:

1) We could report your Asleep start/end time in Health as the same times that Fitbit reports, resulting in a sleep duration in Health that does not match Fitbit
2) We could report the Asleep start time as what Fitbit reports, but then take the Fitbit end time and subtract the number of minutes you were awake in the middle of the night, and use that as the “end time” in Health.

We chose the latter option because this results in a more accurate “average duration” of sleep reported in Health. This will, however, cause Health to make it look like you woke up a little bit earlier than Fitbit reports (if you have less than 100% sleep efficiency). We are definitely open to suggestions on this, or possibly even making it a setting to allow you to choose which way it converts.
Why does it only track one sleep session per day when I have more than one?
The app only supports syncing one sleep session per day at this time.
Why is the sleep analysis off by one day in Health?
There was a known issue in version 1.0 of the app that could cause sleep analysis to show up one day later in some cases. Delete the app, including all Health data, and update to the latest version to correct the issue.
Why is the sleep analysis grouped inconsistently in Health?
Health lists sleep entries according to the end date of the data point. If you go to sleep past midnight, you are technically going sleep on the same day that you are waking up. If you then go to sleep before midnight on that same day, Health will show two sleep entries for the same day. Navigate into the actual sleep entry in Health if you want to see the details of exactly when you went to sleep or woke up on a given day.
What username/password should I use to login?
Sync Solver requires a Fitbit.com user account. If you don't have one already, register here. If you don't remember your password, reset it here.
I just upgraded my phone, where is all my historical data?
Depending on how you upgrade, Apple may not import all the data from Health on your previous phone. If you delete and reinstall Sync Solver, it will bring back all your historical data.
Why does it not sync workouts?
Health and Fitbit store workouts in different formats, so performing a sync between the two is not straight forward. We are still investigating a way to provide this functionality without overburdening users. At the moment it would require a tedious set of dialogs to specify a mapping between the two.
What types of anonymous usage data do you collect and why?
The primary type of anonymous usage data that we collect is error and diagnostic information, which helps us find and correct issues and improve the stability of the app. We also collect performance information, which helps us determine how to make the app faster and more responsive.

Usage data does not, and will never include identifying information or your Health data. If you want to disable sending anonymous usage data, open the iOS Settings app, navigate to Sync Solver > Send Anonymous Usage Data and turn the switch off.
What is your privacy policy?
Our privacy policy can be found by clicking the link at the bottom of this page.
In short, we do not do anything with your Health data other than put it into the Health app after we download it from Fitbit. That is to say, it never leaves your device.
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