Apple Watch Series 3

Built-in LTE and UMTS cellular connectivity (GPS + Cellular tier)

Integrates a full cellular baseband sharing the iPhone's telephone number via carrier network pairing, enabling standalone calls, messaging, and Apple Music streaming without iPhone proximity.

Display-as-antenna RF architecture

Utilizes the OLED display surface itself as both a transmitting and receiving antenna for LTE and UMTS bands, saving internal volume.

Embedded electronic SIM (eSIM)

Integrates an embedded SIM module over one-hundredth the size of a conventional SIM card.

Barometric altimeter sensor

Internal pressure sensor measuring relative elevation changes to track flights of stairs climbed, outdoor elevation gain, and skiing/snowboarding metrics.

Apple S3 dual-core SiP

Up to 70 percent faster dual-core processor, providing sufficient local processing performance for Siri to speak aloud via the internal speaker for the first time.

Apple W2 wireless chip

Delivers up to 85 percent faster Wi-Fi performance while improving Wi-Fi and Bluetooth energy efficiency by 50 percent.

Red cap on Digital Crown

(minor): Visual differentiator featuring a distinctive red surface dot on the crown of cellular-equipped models.

Gray ceramic Apple Watch Edition

(minor): Deep gray ceramic finish added to the luxury Edition collection alongside white ceramic.

Internal storage capacity

Upgraded to 16GB on GPS + Cellular models; standard GPS-only models remained at 8GB.

Case back thickness and composition

(minor): Overall back crystal thickness increased by 0.25mm (~two sheets of paper); all Cellular models featured full ceramic backs, whereas GPS-only models retained composite backs.

Heart Rate tracking capabilities (watchOS 4)

Expanded heart rate analytics to include resting heart rate, walking average heart rate, workout recovery rate, and elevated resting heart rate alerts.

Silent Siri interaction

(minor): Siri gained the capability to speak responses aloud via the speaker rather than relying purely on text on screen.

38mm and 42mm case geometry

Preserved the classic physical case sizes and 100% backward compatibility with all Apple Watch bands.

50-meter water resistance (ISO 22810:2010)

Maintained swimproof rating with acoustic water ejection.

18-hour all-day battery life standard

Maintained 18-hour day rating (including 1 hour of connected cellular talk/workout).