The Apple Watch Series 12 is now available, three years after the Series 9. In that time, Apple has introduced a thinner design, larger displays, faster charging, new water sensors, and a substantially more capable health sensing system. Is that enough to justify replacing a Series 9?
Apple discontinued the Series 9 in 2024. The older watch still supports watchOS 27, so the decision comes down to the hardware and features you would gain. Here are the key differences between the Apple Watch Series 9 and Series 12:
| Apple Watch Series 9 | Apple Watch Series 12 |
|---|---|
| 41mm and 45mm cases, 10.7mm thick | 42mm and 46mm cases, 9.7mm thick in aluminum and titanium; ceramic cases are 9.85mm thick |
| Aluminum or stainless steel case | Aluminum, titanium, or ceramic case |
| Aluminum: Silver, Starlight, Midnight, Pink, and (PRODUCT)RED | Aluminum: Dark Bronze, Light Gold, Black, and Space Gray |
| Stainless steel: Silver, Gold, and Graphite | Titanium: Radiant Gold and Natural Ceramic: Pearl White and Night Blue |
| Ion-X front glass on aluminum models; sapphire crystal on stainless steel models | Ceramic Shield 2 on aluminum models; sapphire crystal on titanium and ceramic models |
| Ceramic and sapphire crystal back | Case-matched metal or ceramic and zirconia back |
| 41mm: 904 sq mm display area 45mm: 1,143 sq mm display area |
42mm: 970 sq mm display area 46mm: 1,196 sq mm display area |
| LTPO OLED Always-On Retina display | LTPO3 wide-angle OLED Always-On Retina display with a 1Hz refresh rate, enabling a live ticking seconds hand on select watch faces |
| S9 chip | S11 chip |
| 2GB RAM | 4GB RAM |
| Electrical heart sensor | Second-generation electrical heart sensor |
| Third-generation optical heart sensor | Fourth-generation, always-on optical heart sensor |
| Periodic background heart rate readings | Background heart rate readings every five seconds |
| Heart rate variability (HRV) measurements | Recovery HRV and overall HRV, measured up to 24 times more frequently |
| Vitals app with overnight health metrics | Vitals app with Recovery HRV and a daytime vitals view |
| Readiness app with a daily score and recommendation | |
| Step tracking | Redesigned step tracking and a Steps watch face complication |
| Wrist temperature sensor | Wrist and water temperature sensors |
| Depth gauge to 6 meters and Depth app | |
| Microphone | Microphone with Voice Isolation |
| Speaker | Redesigned speaker with media playback |
| Audio Intelligence, including Sound Recognition, faster Shazam, Live Rewind, and Siri Recap | |
| LTE and UMTS on cellular models | LTE and 5G RedCap on cellular models |
| Up to 18 hours of normal use; up to 36 hours in Low Power Mode | Up to 24 hours of normal use; up to 38 hours in Low Power Mode |
| Up to 80% charge in about 45 minutes | Up to 80% charge in about 30 minutes; 15 minutes of charging provides up to 12 hours of normal use |
| Now discontinued | From $399 |
Design
The Series 12 uses a similar version of the thinner design introduced with the Series 10. Its display area is about 7% larger in the smaller size and 5% larger in the larger size than the corresponding Series 9 models. The Series 12 figures below are for aluminum models; its ceramic cases are slightly larger and heavier:
| Apple Watch Series 9 | Apple Watch Series 12 | |
|---|---|---|
| Smaller case | 41mm × 35mm × 10.7mm | 42mm × 37mm × 9.7mm |
| Larger case | 45mm × 38mm × 10.7mm | 46mm × 40mm × 9.7mm |
| Smaller aluminum model, GPS | 31.9 grams | 32.2 grams |
| Larger aluminum model, GPS | 38.7 grams | 39.5 grams |
| Smaller aluminum model, cellular | 32.1 grams | 31.5 grams |
| Larger aluminum model, cellular | 39.0 grams | 38.6 grams |
The Series 12 is noticeably thinner, but the comparable aluminum GPS models are slightly heavier than their Series 9 counterparts. Buyers moving from a stainless steel Series 9 to a titanium Series 12 will see a more substantial weight reduction because the case material has changed.
Is It Worth Upgrading?
For Series 9 owners, the Series 12 is a meaningful cumulative upgrade, particularly if you use your watch for training and recovery. Its more frequent heart rate and HRV readings support Readiness, Recovery HRV, and daytime vitals, while the redesigned case provides a larger, squarer display with a more modern feel. The depth gauge and water temperature sensor also add useful information for swimmers and snorkelers.
Those improvements are less compelling if you mainly use your watch for notifications, everyday activity tracking, and occasional workouts. The Series 9 still has an always-on display, ECG, wrist temperature sensing, Double Tap, sleep apnea and hypertension notifications, and support for watchOS 27. Siri AI is also available on the Series 9 when paired with a compatible iPhone.
The Series 12 also has a slightly larger battery and charges faster, but likely not by enough to justify an upgrade alone. The Series 12's Audio Intelligence features may strengthen the case for some users, especially Sound Recognition for people who are deaf or hard of hearing. Live Rewind and Siri Recap will arrive in beta in late 2026.
Which to Buy Today?
For a new purchase, the Series 12 is clearly the better choice. It offers three generations of accumulated improvements at the same $399 starting price the Series 9 had when new. The older model makes sense only at a substantial discount if you are satisfied with its existing health features.
A used or refurbished Series 9 can still be good value, but check its battery health, physical condition, and warranty before comparing prices. A worn battery could quickly erase the saving.
