Google Health API data types

The following table contains the full list of data types, with several columns to help you understand the representation of each type in the Google Health API, as well as the scope each is available under.

Note: Fitbit Ace devices are not supported by the Health API. For more information, see Fitbit Privacy Policy for Children's Accounts.

Important: The format of data type identifiers differs when the data type has more than one word. In an endpoint, the data type name must be in kebab case, such as body-fat. In a filter parameter, however, the data type name must be in snake case, such as body_fat.

Table: Google Health API data types

Data type   dataType   filter parameter	Available operations	Scope
Active Energy Burned active-energy-burned active_energy_burned Record type: Interval Calories and energy guide	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Active Minutes active-minutes active_minutes Record type: Interval Compatible devices Fitbit Air Fitbit Alta Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Flex 2 Fitbit Inspire Fitbit Inspire HR Pixel Watch 4	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Active Zone Minutes active-zone-minutes active_zone_minutes Record type: Interval Webhook support Compatible devices Fitbit Air Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Activity Level activity-level activity_level Record type: Interval Webhook support	list, reconcile	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Altitude altitude altitude Record type: Interval Webhook support True zeros support	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Blood Glucose blood-glucose blood_glucose Record type: Sample Webhook support Vitals guide	list, get, reconcile, rollup, dailyRollup	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Body Fat body-fat body_fat Record type: Sample Webhook support Compatible devices Fitbit Aria Fitbit Aria 2 Fitbit Aria Air	list, get, reconcile, rollup, dailyRollup, create, update, batchDelete	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Calories In Heart Rate Zone calories-in-heart-rate-zone calories_in_heart_rate_zone Record type: Interval Webhook support	rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Core Body Temperature core-body-temperature core_body_temperature Record type: Sample Vitals guide	list, get, reconcile, rollup, dailyRollup	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Daily Heart Rate Variability daily-heart-rate-variability daily_heart_rate_variability Record type: Daily Webhook support Vitals guide Sleep guide Compatible devices Fitbit Air Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4	list, reconcile	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Daily Heart Rate Zones daily-heart-rate-zones daily_heart_rate_zones Record type: Daily Webhook support Vitals guide	list, reconcile	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Daily Oxygen Saturation daily-oxygen-saturation daily_oxygen_saturation Record type: Daily Webhook support Vitals guide Sleep guide Compatible devices Fitbit Air Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 3 Fitbit Ionic Fitbit Luxe Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4	list, reconcile	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Daily Respiratory Rate daily-respiratory-rate daily_respiratory_rate Record type: Daily Webhook support Vitals guide Sleep guide Compatible devices Fitbit Air Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4	list, reconcile	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Daily Resting Heart Rate daily-resting-heart-rate daily_resting_heart_rate Record type: Daily Webhook support Vitals guide Compatible devices Fitbit Air Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Daily Sleep Temperature Derivations daily-sleep-temperature-derivations daily_sleep_temperature_derivations Record type: Daily Webhook support Vitals guide Sleep guide Compatible devices Fitbit Air Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4	list, reconcile	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Daily VO2 Max daily-vo2-max daily_vo2_max Record type: Daily Compatible devices Fitbit Air Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Distance distance distance Record type: Interval Webhook support True zeros support Compatible devices Fitbit Air Fitbit Alta Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Flex 2 Fitbit Inspire Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Fitbit MobileTrack Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Electrocardiogram (ECG) electrocardiogram electrocardiogram Record type: Session Vitals guide Compatible devices Fitbit Charge 5 Fitbit Charge 6 Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2	list	.ecg.readonly
Exercise exercise exercise Record type: Session Webhook support Workouts guide Compatible devices Fitbit Air Fitbit Alta Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Flex 2 Fitbit Inspire Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Fitbit MobileTrack Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, get, reconcile, create, update, batchDelete	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Floors floors floors Record type: Interval Webhook support True zeros support	reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Food food food Record type: Food Nutrition guide	list, get	.nutrition.readonly .nutrition.writeonly
Food Measurement Unit food-measurement-unit food_measurement_unit Record type: Food Nutrition guide Compatible devices Fitbit Air Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Ionic Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4	list, get	.nutrition.readonly .nutrition.writeonly
Heart Rate heart-rate heart_rate Record type: Sample Webhook support Vitals guide Compatible devices Fitbit Air Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile, rollup, dailyRollup	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Heart Rate Variability heart-rate-variability heart_rate_variability Record type: Sample Webhook support Vitals guide Sleep guide Compatible devices Fitbit Air Fitbit Alta Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Flex 2 Fitbit Inspire Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Fitbit MobileTrack Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Height height height Record type: Sample Webhook support	list, get, reconcile, create, update, batchDelete	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Hydration Log hydration-log hydration_log Record type: Session Webhook support	list, get, reconcile, rollup, dailyRollup, create, update, batchDelete	.nutrition.readonly .nutrition.writeonly
Irregular Rhythm Notification irregular-rhythm-notification irregular_rhythm_notification Record type: Session Vitals guide	list	.irn.readonly
Menstrual Period menstrual-period menstrual_period Record type: Interval	create, update, batchDelete	.reproductive_health.writeonly
Moods moods moods Record type: Sample	create, update, batchDelete	.mindfulness.writeonly
Nutrition Log nutrition-log nutrition_log Record type: Sample Webhook support Nutrition guide Compatible devices Fitbit Air Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, get, reconcile, rollup, dailyRollup, create, update, batchDelete	.nutrition.readonly .nutrition.writeonly
Ovulation Test ovulation-test ovulation_test Record type: Sample	create, update, batchDelete	.reproductive_health.writeonly
Oxygen Saturation oxygen-saturation oxygen_saturation Record type: Sample Vitals guide Sleep guide Compatible devices Fitbit Air Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 3 Fitbit Ionic Fitbit Luxe Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4	list, reconcile	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Respiratory Rate Sleep Summary respiratory-rate-sleep-summary respiratory_rate_sleep_summary Record type: Sample Webhook support Vitals guide Sleep guide Compatible devices Fitbit Air Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4	list, reconcile	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly
Run VO2 Max run-vo2-max run_vo2_max Record type: Sample Webhook support Compatible devices Fitbit Air Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Sedentary Period sedentary-period sedentary_period Record type: Interval Webhook support Compatible devices Fitbit Air Fitbit Alta Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Flex 2 Fitbit Inspire Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Fitbit MobileTrack Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Sleep sleep sleep Record type: Session Webhook support Sleep guide Compatible devices Fitbit Air Fitbit Alta Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Flex 2 Fitbit Inspire Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, get, reconcile, create, update, batchDelete	.sleep.readonly .sleep.writeonly
Steps steps steps Record type: Interval Webhook support True zeros support Steps guide Compatible devices Fitbit Air Fitbit Alta Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Flex 2 Fitbit Inspire Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Fitbit MobileTrack Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Swim Lengths Data swim-lengths-data swim_lengths_data Record type: Interval Compatible devices Fitbit Air Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Flex 2 Fitbit Inspire Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Symptoms symptoms symptoms Record type: Sample	create, update, batchDelete	.logged_symptoms.writeonly
Time in Heart Rate Zone time-in-heart-rate-zone time_in_heart_rate_zone Record type: Interval Webhook support	list, reconcile, rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Total Calories total-calories total_calories Record type: Interval True zeros support Calories and energy guide Compatible devices Fitbit Air Fitbit Alta Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Flex 2 Fitbit Inspire Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Inspire HR Fitbit Ionic Fitbit Luxe Fitbit MobileTrack Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	rollup, dailyRollup	.activity_and_fitness.readonly .activity_and_fitness.writeonly
VO2 Max vo2-max vo2_max Record type: Sample Compatible devices Fitbit Air Fitbit Alta HR Fitbit Blaze Fitbit Charge 2 Fitbit Charge 3 Fitbit Charge 4 Fitbit Charge 5 Fitbit Charge 6 Fitbit Inspire 2 Fitbit Inspire 3 Fitbit Ionic Fitbit Luxe Pixel Watch Pixel Watch 2 Pixel Watch 3 Pixel Watch 4 Fitbit Sense Fitbit Sense 2 Fitbit Versa Fitbit Versa 2 Fitbit Versa 3 Fitbit Versa 4 Fitbit Versa Lite	list, reconcile	.activity_and_fitness.readonly .activity_and_fitness.writeonly
Weight weight weight Record type: Sample Webhook support Compatible devices Fitbit Aria Fitbit Aria 2 Fitbit Aria Air	list, get, reconcile, rollup, dailyRollup, create, update, batchDelete	.health_metrics_and_measurements.readonly .health_metrics_and_measurements.writeonly

Query constraints

When querying data points, rollups, or daily rollups from the API, keep the following constraints in mind:

• Filter requirements: Some read-only derived data types, such as total-calories, require a filter specifying an interval start time (using physical or civil time).
• Query range limits: Rollup and daily rollup aggregation endpoints enforce maximum query range limits based on the data type:
  • A maximum query range of 14 days for calories-in-heart-rate-zone, heart-rate, active-minutes, and total-calories.
  • A maximum query range of 90 days for all other data types.

Data availability

Updates to the user's data is only available after they sync their activity tracker or manually enter new data into the Fitbit mobile or web app. The Fitbit device and Fitbit mobile app can automatically sync every 15 minutes when the Fitbit app is open on the mobile device and the two have an active data connection and are within Bluetooth range. If the user is tracking activity using MobileTrack, MobileTrack syncs every hour as long as the app is open.

Querying historical data

One of the core benefits of the Google Health API is the ability to track a user's performance and monitor their health vitals over long periods of time. You can query a user's data as far back as it has been recorded; the API imposes no limitations or restrictions on the amount of historical data your application can consume.

However, querying historical data is still governed by standard rate limits. To manage system stability and prevent excessive payloads, the Google Health API uses automatic pagination with endpoint-specific page sizes. Note the following boundaries and behavior:

• Automatic pagination: If you query a long span of data, the API will only return the first page of results up to the page size cap for that endpoint, along with a nextPageToken. You must use the nextPageToken to request subsequent pages.
• Variable page sizes: Capping limits depend on the endpoint and data type. For most data types, page sizes are capped at a maximum of 10,000. However, for certain data types like exercise and sleep, the default and maximum page size is capped at 25. For example, if a client requests all sleep data for the past 10 years, the API will still return only 25 sleep sessions on the first page.
• Rollup date range restrictions: For data rollup and aggregation endpoints (such as rollUp and dailyRollUp), query date ranges are restricted based on the data type:
  • A maximum range of 14 days for calories-in-heart-rate-zone, heart-rate, active-minutes, and total-calories.
  • A maximum range of 90 days for all other rollup data types.

Depending on the volume of historical data your application needs, retrieving the entire dataset will require paginating through the pages sequentially. Keep this in mind when designing your application's data synchronization process.

To ensure optimal performance and avoid API errors, follow these guidelines when querying historical data:

Phased data sync (hot versus cold load)

• Initial "hot" load: Fetch and render only the most recent 7–14 days of data during the primary load sequence. This ensures that users see data immediately without waiting for long-running queries.
• Background "cold" load: Delegate older historical data retrieval to an asynchronous, lower-priority queue or background process after the primary UI is rendered.

Query chunking for aggregation

• Because rollup and daily rollup endpoints enforce a maximum date range limit (14 or 90 days depending on the data type), you must break down large historical aggregation queries into smaller, sequential intervals within these limits.
• Batch or sequence these sub-queries safely to respect concurrency limits and maintain steady UI progress indicators.

Leverage pre-aggregated roll-ups

Restructure overview dashboards and trend charts to use pre-aggregated, summary endpoints (such as DailyRollUpDataPoints). This will drastically reduce compute overhead on the backend and network transfer time to the client.

Resilient error handling (smart retries)

• Implement strict exponential backoff handling when encountering rate limits (429 Too Many Requests) and server gateway timeouts (504 Gateway Timeout). Never retry large, failed payloads immediately. Instant retries multiply backend congestion and compound system degradation.

Warning: Not following these guidelines can introduce unexpected behavior and errors.

Third-party access

Fitbit devices can't communicate directly with third-party applications or services. These devices are designed to communicate and synchronize exclusively with the Fitbit mobile app.

The device syncs data automatically throughout the day, whenever the Fitbit app is open, or every 15 minutes if Bluetooth is active and the app is running in the background. Once this synchronization process is complete, the data is then available for third-party services through the Google Health API.

Distance standards

Exercise distances, such as elevationGainMillimeters, are measured in millimeters as the standard unit for the following reasons:

1. Maintaining Data Precision: The most important reason for using millimeters is to ensure we don't lose any precision in the data we read and provide. Using a fine-grained unit like millimeters allows us to represent measurements with high accuracy.
2. Standardization: Millimeters are the designed standardized unit across our services. This consistency helps ensure a uniform experience for developers interacting with different parts of the API.
3. Broad Measurement System Support: Using a base unit like millimeters makes it straightforward for developers to convert to any other chosen unit, regardless of whether they are working with metric, imperial, or other measurement systems.

Variable day lengths

Time handling by the Health API prioritize the user's time to account for variable day lengths caused by Daylight Savings Time or travel. Every data point is stored with both a physical UTC timestamp and the UTC offset active at the time of the event. This allows the system to:

• Map the event to a precise physical instant.
• Correct the time to the user's local context for aggregation.

Daylight Savings Time

When Daylight Savings Time happens, a "fall back" results in a 25-hour civil day, and the rollup for that date will contain 25 hours of data. A "spring forward" results in a 23-hour civil day where the time moves back to Standard Time.

Travel

Travel across time zones can cause even more significant variations in the physical duration of a single civil day.

Use the dailyRollUp endpoint to reconcile time zone differences. It automatically attributes data to the calendar day on which it was recorded according to the user's local time, effectively "stitching" the day together despite time zone shifts.