APIs and SDKs are often mentioned in the same breath, but in digital health, the difference between them is more than just technical, it defines how your app functions, scales, complies with regulations, and integrates with the world’s most fragmented wearable ecosystem. Whether you’re building a health platform, an insurance program, or a digital therapeutic, choosing between an SDK and an API shapes everything from development time and data quality to user experience and long-term reliability.
Generally, an API connects your system to a data source or service through the cloud, while an SDK embeds pre-built components directly into your mobile app. But when real-time health data, compliance frameworks, and device permissions enter the picture, the trade-offs become far more significant.
We already talked about health data integration in health apps. Today, we break down the practical differences between APIs and SDKs, explain when each option offers the most value, and highlight the unique considerations for health apps that must operate safely, securely, and at scale. By the end, you’ll have a clear framework to choose the right integration path for your product and avoid costly mistakes later on.
An API (Application Programming Interface) is a cloud-based interface that allows your app to request and receive data from an external service. Instead of storing data or processing it locally, your application “asks” the API for information, such as steps, heart rate, HRV, sleep, or device metadata, and receives the processed data back through secure endpoints.
In digital health, APIs act as the bridge between wearable ecosystems (Apple Health, Health Connect, Garmin, Fitbit, Oura, medical devices, etc.) and your backend. They allow your servers to fetch standardized health data, synchronize updates, and manage user connections through OAuth or similar authorization frameworks.
Because APIs operate server-to-server, they offer strong advantages for regulated products:
The downside is that APIs depend on stable connections and cloud availability. They cannot collect certain data types that are only accessible directly from the device sensors, and they may introduce minor latencies in fast-moving use cases like real-time workout visualization.
Overall, APIs excel for products that need scalability, strong compliance workflows, and consistent multi-device support, without managing device-level integrations on their own.
An SDK (Software Development Kit) is a bundle of tools, libraries, and device-specific logic that lives directly inside your mobile app. Unlike APIs, which fetch data from the cloud, an SDK runs locally on the user’s device, giving you deeper access to hardware features and raw sensor streams. This is why SDKs are widely used in apps that require high-frequency, low-latency, or device-native capabilities.
With an SDK, your app can interact directly with device sensors such as PPG, accelerometers, gyroscopes, GPS, skin temperature probes, or Bluetooth connections. This enables advanced real-time connections, like continuous heart rate monitoring during workouts, live movement classification, gait analysis, or fall detection. Because everything happens locally, apps can respond instantly, even without internet access.
Some key advantages of SDKs include:
However, SDKs come with heavier engineering demands. Each device brand may require separate integration work, separate maintenance cycles, and separate testing processes. There are also compliance considerations: storing or processing raw health data locally can increase your regulatory responsibilities.
In short, SDKs are best suited for applications that need real-time data, sensor-level access, or device-native experiences, not broad, multi-device health data aggregation. If your product relies on advanced performance metrics, on-device analytics, or hardware-specific features, an SDK-based approach can unlock functionality that APIs simply cannot provide.
Choosing between an API and an SDK is one of the first steps in creating your health app. While both approaches enable health data integration, they differ significantly in how they operate and what they demand from your team.
APIs offer simplicity. They are easier to implement, maintain, and scale across hundreds of devices because all processing happens in the cloud. Developers avoid device-level complexity and rely on aggregated, standardized data models. This accelerates development, reduces maintenance overhead, and ensures consistent compliance since sensitive processing never occurs on the user’s device.
SDKs, by contrast, require deeper investment. They operate directly on the phone or wearable, giving access to raw sensor streams but also demanding more engineering expertise, heavier testing, and device-by-device optimization. They offer the highest customization and control, but they also increase battery consumption risk and require ongoing maintenance as operating systems evolve.
Key differences that matter:
The right choice depends on your product’s depth of analytics, regulatory needs, and engineering capacity.
Health apps face challenges that go far beyond what typical consumer apps deal with. The combination of medical-grade expectations, strict regulations, and fragmented wearable ecosystems means your choice between SDK and API can determine whether your product scales smoothly or breaks under pressure.
Apple Watch, Garmin, Fitbit, Oura, Polar, Samsung, and dozens of others each use different sensors, algorithms, permissions, sampling rates, and sync behaviors. An SDK must account for all this complexity on-device, while an API abstracts it away, which dramatically influences your development workload.
Apple HealthKit, Google Health Connect, and manufacturer APIs all impose different consent rules, access scopes, and data-sharing constraints. Choosing the wrong integration layer can lead to missing data, broken sync flows, or rejected app updates.
Health apps must also comply with GDPR, HIPAA, and sometimes MDR. SDKs may require local storage or processing on the device, which increases your compliance burden. APIs centralize governance and offer clearer auditability. For more information, check our blog post on health data regulations!
Signal noise, sampling gaps, and device-specific quirks can break algorithms if not normalized. Using the wrong method, especially raw SDK access without proper smoothing or thresholding, frequently results in outages, data corruption, or inconsistent insights.
Choosing between an SDK and an API is one of the most important architectural decisions a health product team can make. The right choice depends on your accuracy needs, development resources, regulatory obligations, and long-term scalability goals. For example, Thryve is built as an API-first platform, but we support SDK-based workflows where they make sense, giving product teams the flexibility to choose the right method without dealing with the underlying complexity of health data ecosystems. In most cases, teams benefit from a hybrid model, and Thryve makes that possible without the usual fragmentation or instability. With us, you get:
Whether you start with the SDK or the API, Thryve makes it easy to switch approaches as your product matures. The result is a flexible, future-proof foundation that supports innovation without compromising reliability or compliance. Check here what happens to your data in Thryve!
Book a demo to see how our platform simplifies both SDK and API workflows.
Friedrich Lämmel is CEO of Thryve, the plug & play API to access and understand 24/7 health data from wearables and medical trackers. Prior to Thryve, he built eCommerce platforms with billions of turnover and worked and lived in several countries in Europe and beyond.
