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Frequently Asked Questions

Data and internet access

  • Does Cozie work without an internet connection?

    No, Cozie needs at least internet access during the setup phase. After the initial setup, some features can be used without internet access.

    • These features work without an internet connection:
      • Watch surveys after initial setup
      • Offline logging to local file (watch survey & health data)
      • Watch survey reminders
      • Phone survey reminders
    • These features require an internet connection:
      • Watch surveys (during setup)
      • Logging to the online database (watch survey & health data)
      • Feedback information shown in the Data tab, e.g., Valid Survey Count, Invalid Survey Count, Last Watch Survey
      • Links shown in the Data tab, e.g., Cozie Github Repository, Cozie Documentation
      • Phone survey
      • Push notifications
  • Do the reminders work without an internet connection?

    Yes, all reminders work without an internet connection. Please note that while the phone survey reminder works without an internet connection, the phone survey itself requires an internet connection.

  • Does the Apple Watch have to be connected to the iPhone for Cozie to work?

    We have only tested Cozie Apple exclusively on Apple Watches without a modem. While the Apple Watch is not connected to the iPhone, the watch survey response will be saved on the Apple Watch. The response will be sent to the database once the Apple Watch connects again to the iPhone. The same applies to health data.

    Reminders won't be shown on the Apple Watch if the watch is not connected to the iPhone.

  • Where is Cozie data stored?

    Cozie offers two ways to store data:

    1. Default
      By default, Cozie-Apple data is stored on password-protected servers in Singapore and logged on the iPhone. The data can be downloaded from our online API. Data data can also be retrieved from the local backup file.

    2. Custom Database
      Instead of using our database to store your data, you can also set up your own backend. Just replace the necessary information about the API and OneSignal in the Backend tab and you can operate the Cozie app independent of us. No changes to the source code are required. Screenshot backend tab default API and OneSignal configuration  


  • How long does it take for a push notification from OneSignal to arrive on the iPhone or Apple Watch?

    Provided there is an internet connection, it usually takes less than ten seconds between sending a push notification, and the push notification appearing on the iPhone and/or the Apple Watch.

  • How frequently is the physiological data logged?

    It is important to distinguish two terms: logging rate and sampling rate. The sampling rate is defined by the time between to measurement samples. The logging rate is defined by the points in time when the measurement samples were sent to the database.


    2023-10-10 12:49762023-10-10 12:53background_task
    2023-10-10 12:52752023-10-10 12:53background_task
    2023-10-10 12:55772023-10-10 13:15application_appear

    The table above shows three samples of a heart rate measurement (ts_heart_rate). The ts_heart_rate column shows the value of the measurement in beats per minute (bpm).

    The time column shows when the measurement took place.

    The ts_heart_rate_lambda column shows the timestamp of when the sample was inserted into the database (logged).

    The ts_heart_rate_trigger column records what triggered the Cozie app to send the data.

    In this example, the timestamps in time are three minutes apart. Hence, the sampling rate is 1 sample per 3 minutes.

    The first two rows were logged at the same time (tes_heart_rate_lambda). The third row was logged 23 minutes later. Hence, the logging rate is 1 log per 23 minutes. The sampling rate cannot be influenced is given by the data provided by iOS. The logging rate can be influenced, e.g., by opening the app, using the iPhone, and taking watch surveys.

  • Is it possible to call the function that pulls the GPS location, heart rate data, etc in a set interval without the participant interacting with the survey?

    Well, having a live stream of all data is the dream. We've been hard working on that dream for a while. Here is the result: All HealthKit data is submitted twice:

    1. When the watch survey is submitted. In that case, the prefix is ws_, e.g., ws_heart_rate.
    2. Then the HealthKit data is submitted a second time with the prefix ts_, e.g., ts_heart_rate.

    ts_ data has various triggers, e.g., when you open the app, when press the sync buttons in the app, sometimes it is sent in the background.

    You can check what triggered the transmission of the data and when it arrived in the database with the fields with the postfix _trigger and _lambda, e.g., ts_heart_rate_trigger and ts_heart_rate_lambda or ws_heart_rate_trigger and ws_heart_rate_lambda.

    You can increase the chances of the data being sent by using the iPhone. Because Cozie can only access HealthKit data when the phone is unlocked. But in our experience, the ws_ data has the highest update frequency provided participants are reminded every hour and also provide a watch survey response accordingly.

    For the location, you already know about ws_latitude and ws_longitude. There is also ts_latitude, and ts_longitude. These location data are sent when the user changes their location.

  • How long does it take for a watch survey to be stored in the online database?

    Provided there is an internet connection, it usually takes less than ten seconds between pressing the 'Submit survey' button and the response being logged in the database.

  • What is the minimum and maximum reminder frequency?

    The minimum time between two reminders is 30 minutes.
    The maximum time between two reminders is 24 hours.
    The maximum of total reminders per week is 64, e.g., if reminders are set every hour from 9 am to 6 pm and Monday through Friday that adds up to 10 reminders per day times 5 days, totalling 50 reminders. Phone survey reminders also count towards the maximum of 64 reminders per week.

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