The Apple Watch Series 3 introduced a new era of connected health and fitness, building on the original design with faster performance and expanded LTE options. Its successor, the Apple Watch Series 4, refined those strengths with a larger display, advanced sensors, and a more premium build. This overview highlights how those updates translate into real-world use.
Both devices remain relevant for users focused on reliable health metrics, clear navigation, and long-term software support from Apple.
| Aspect | Series 3 | Series 4 | Key Takeaway |
|---|---|---|---|
| Display Size | 1.3-inch diagonal | 1.4-inch diagonal | Larger, easier-to-read interface on Series 4 |
| Processor | S3 SiP with dual-core processor | S4 SiP with 64-bit dual-core processor | Improved speed and efficiency in Series 4 |
| Built-in GPS | Available in GPS + Cellular models | Available in all models | More flexible outdoor tracking options in Series 4 |
| Electrical Heart Sensor | No | Yes, with ECG app support | Series 4 adds heart rhythm insights and irregular notifications |
| Design and Materials | Aluminum back with Series-branded band clips | Surgical-grade aluminum back, larger corner curves | Series 4 feels more premium and modern |
Design and Display Upgrades
Series 4 brought noticeable refinements to the chassis, improving everyday handling. The display extends further to the edges, reducing bezels and making notifications and apps more readable at a glance. The back case curves more naturally around the wrist, which can improve comfort during long wear sessions. These physical changes mark a clear step forward in polish and usability.
Performance and Processing Enhancements
The S4 SiP in Series 4 delivers faster app launches, smoother animations, and better power management compared to the S3 chip in Series 3. Complex workouts with multiple metrics, plus background tasks, run more seamlessly. This performance bump supports newer software features and longer battery cycles without sacrificing responsiveness.
Health and Sensor Innovations
Series 3 established strong fundamentals for heart rate tracking and activity monitoring. Series 4 pushed further with an electrical heart sensor that enables on-demand ECG readings and irregular rhythm notifications. These additions make the device more proactive in highlighting potential heart-related concerns, broadening its appeal for health-conscious users.
Battery and Connectivity Options
Both generations offer competitive battery life with consistent all-day performance. Series 4 expanded connectivity by including GPS and cellular capabilities in more configurations, giving users flexibility to leave their phone behind during runs or commutes. Enhanced background app refresh and improved Wi-Fi selection keep connections smooth and efficient.
Key Takeaways and Recommendations
- Series 4 offers a more modern design with a larger, edge-to-edge display.
- Processing and health sensors are meaningfully improved in Series 4.
- Series 3 remains a solid choice for core fitness tracking and daily notifications.
- Consider Series 4 if ECG, advanced health alerts, and premium materials are priorities.
FAQ
Reader questions
Does the Series 4 heart sensor work without using third-party apps?
The ECG app is built into watchOS and guides users through taking a reading, with results flagged for irregular rhythms directly on the device.
Is the larger display on Series 4 significantly easier to use than Series 3?
Yes, the bigger screen with reduced bezels makes reading messages, checking workouts, and navigating apps noticeably clearer on Series 4.
Are Apple Watch Series 3 and Series 4 interchangeable in terms of bands?
They share the same band sizes and attachment system, so most sport, solo loop, and braidable bands will fit both models.
Does upgrading from Series 3 to Series 4 offer meaningful day-to-day improvements?
Users will notice faster performance, a cleaner display, and the added heart health features, especially if they value ECG and irregular rhythm alerts.