Smartwatch Operating Systems - Everything You Need to Know

Which Operating System is Used in Smartwatches?

Smartwatch Market for High-Level Operating System

Source: Counterpoint study

Smartwatches are categorized by their operating system architecture:

1 • High-Level Smartwatch Operating Systems (HLOS)

These are sophisticated platforms capable of running third-party applications, providing rich graphical user interfaces, and enabling advanced features like voice assistants, music streaming, contactless payments, and health tracking. Examples include:

• Apple watchOS
• Google Wear OS
• Huawei HarmonyOS

While these offer a polished and feature-rich experience, they come with trade-offs:

• Higher hardware requirements, meaning increased BoM (bill of materials) cost
• Battery life is typically capped at 1–3 days
• Heavier firmware packages and limited flexibility for deep hardware optimization

2 • Real-Time Operating Systems (RTOS) or Lightweight Custom OS

RTOS-based platforms focus on simplicity, ultra-low power consumption, and fast real-time performance. These are ideal for fitness trackers and basic smartwatches where longevity and cost are more important than app stores or third-party support. Examples include FreeRTOS, Zephyr Project, or custom OSes in Garmin, Suunto, Amazfit, etc.

Pros:

• Battery life of 10+ days, sometimes even weeks or months
• Low hardware demands
• Efficient for simple use cases like steps, heart rate, and notifications

Cons:

• Limited app ecosystem or third-party support
• Hard to evolve or upgrade over time
• Limited UI customization or branding options

Which Smartwatch Operating System has the Largest Market Share?

According to Counterpoint Research (2024):

• Apple watchOS remains the global leader, especially in North America and Europe
• Google Wear OS is gaining ground outside China with a projected 27% market share, powered by Samsung, Pixel, OnePlus, OPPO, and Xiaomi
• Huawei HarmonyOS leads in China, forecasted to reach 61% share, thanks to strong integration with Huawei’s 5G smartphones

While top-tier HLOS platforms dominate the feature-rich segment, a significant portion of global smartwatch volume remains concentrated in the budget and mid-range markets. In fact, a 2024 smartwatch market study by Counterpoint shows that roughly 50% of smartwatches were based on RTOS or hybrid solutions like VEE Wear.

Source: Counterpoint study

What Operating System Does Smartwatches Brands Use?

• Amazfit smartwatches are based on a propriety operating system called Zepp OS is a lightweight smartwatch operating system developed by Zepp Health, programmed in JavaScript with JSON-based UI, supports third-party apps via the Zepp App Store, and offers a limited but straightforward development experience optimized for low-power devices.
• Fitbit smartwatches run on Fitbit OS, a proprietary operating system built by Fitbit using JavaScript for app development, optimized for fitness tracking and long battery life, and still used in recent models like Sense 2 and Versa 4 despite Google’s acquisition.
• Garmin develops its own smartwatch operating system using a proprietary programming language called Monkey C. While explicitly designed for Garmin devices, Monkey C offers limited flexibility, meaning developers must build apps from scratch to ensure compatibility with Garmin watches.
• Huawei smartwatches, including the Watch 3, GT 4, and Watch Ultimate, run on HarmonyOS; Huawei’s proprietary operating system launched in 2021 and now updated to HarmonyOS 5.0, offering seamless device integration and advanced health features.
• Polar smartwatches (as well as upcoming Reebok watches) are powered by VEE Wear, a lightweight operating system by MicroEJ that enables advanced features, third-party app support, and extended battery life on cost-efficient hardware.
• Samsung smartwatches initially ran on Tizen OS, but starting with the Galaxy Watch4, they switched to Google’s Wear OS integrated with Samsung’s One UI Watch, offering broader app support and deeper Android integration across more recent models.
• Apple Watches run on watchOS, Apple’s proprietary operating system designed specifically for wearables. Built on the same foundation as iOS, watchOS offers seamless integration with the Apple ecosystem, featuring optimized apps, health and fitness tracking, and deep connectivity with iPhone, iCloud, and Apple services.
• While Xioami’s Watch 2 Pro and Watch 2 models run on Wear OS by Google, other models, such as the Xiaomi Watch S3, utilize HyperOS, Xiaomi’s proprietary lightweight operating system designed for IoT devices. HyperOS is based on the Xiaomi Vela framework and the NuttX RTOS kernel.

Which Programming Languages is Used in Smartwatches?

Smartwatches use a variety of programming languages depending on the operating system and device manufacturer:

• Apple watchOS: Uses Swift and Objective-C, developed in Xcode with SwiftUI or WatchKit for the UI.
• Fitbit OS: Uses JavaScript for app logic, SVG/Canvas for graphics, and JSON for UI layout via the Fitbit SDK.
• Google Wear OS: Built on Android, it uses Java and Kotlin, with Android Studio as the primary development environment.
• HarmonyOS (Huawei): Uses JavaScript or eTS (extended TypeScript) with Huawei’s own development suite called DevEco Studio.
• MicroEJ VEE Wear: Supports Java, JavaScript, C and C++ (RUST in the future) and allows integration of third-party native C libraries using the Managed-C extension.
• Tizen OS (older Samsung watches): Uses C and HTML5/JavaScript with the Tizen Studio SDK.
• Zepp OS (Amazfit): Uses JavaScript and JSON, similar to Fitbit, offering a lightweight, web-style development approach.
• RTOS-based smartwatches (e.g., Suunto 9/5/3): Typically developed in C or C++, with no third-party app support and limited SDK availability.
• Dual-OS smartwatches (emerging trend): Combine C/C++ for low-level RTOS functions and Java/Kotlin or JavaScript for HLOS-level apps, depending on the main OS.

Which Smartwatch Operating System is Best?

A key industry shift is the rise of dual-OS and dual-chipset architectures, blending high-performance cores with low-power coprocessors. Companies like MicroEJ are leading this evolution thanks to an optimized app-based architecture offering Android compatibility. It depends on your priorities:

Need Rich Apps + Design?

Go with watchOS or Wear OS

Need Max Battery + Low Cost?

Choose RTOS-based systems

Want It All?

Choose VEE Wear:
Rich UX, app support, and long battery life

Summary Table: Comparing Smartwatch OS Options