Apple Watch Series 4 vs Apple Watch Series 6

Every spec side by side, from each maker's published figures.

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Watch Series 4 compared with Watch Series 6

	AppleWatch Series 4	AppleWatch Series 6
Overview
Released
Released	September 2018	September 2020
Display
Case sizes
Case sizes	40 mm or 44 mm	40 mm or 44 mm
Panel
Panel	LTPO OLED	LTPO OLED
Peak brightness
Peak brightness	1,000 nits	1,000 nits
Always-on display
Always-on display	No	Yes
Display detail
Display detail	Retina LTPO OLED with Force Touch; 40mm 324 x 394 pixels and 759 sq mm; 44mm 368 x 448 pixels and 977 sq mm; display wakes by wrist raise (PhoneArena)	Always-On Retina LTPO OLED; 40mm 324 x 394 pixels and 759 sq mm; 44mm 368 x 448 pixels and 977 sq mm; wrist-down outdoor brightness up to 2.5 times Series 5
Health and fitness
ECG
ECG	Yes	Yes
Blood oxygen
Blood oxygen	No	Yes
Skin temperature
Skin temperature	No	No
Sleep apnoea alerts
Sleep apnoea alerts	No	No
High blood pressure alerts
High blood pressure alerts	No	No
Body composition
Body composition	No	No
Fall detection
Fall detection	Yes	Yes
Crash detection
Crash detection	No	No
GPS
GPS	Single-band	Single-band
Water resistance
Water resistance	50 m	50 m
Sensors
Sensors	Electrical and optical heart sensors; barometric altimeter; accelerometer up to 32 g-forces, improved gyroscope and ambient light sensor	Blood oxygen sensor; electrical and third-generation optical heart sensors; compass, always-on altimeter, accelerometer up to 32 g-forces, gyroscope and ambient light sensor
Health features
Health features	ECG capability, high and low heart-rate alerts and irregular-rhythm notifications; ECG app was not available at hardware launch and reached the UK in March 2019	ECG and Blood Oxygen apps, irregular-rhythm notifications; sleep tracking and automatic handwashing detection in watchOS 7; oxygen readings are for general wellness rather than medical use
Fitness features
Fitness features	GPS, GLONASS, Galileo and QZSS; swimming, yoga and hiking workouts, automatic workout reminders, cadence, pace alerts and rolling mile pace in watchOS 5; GymKit	GPS/GNSS and GymKit; always-on elevation tracking; dance, core training, functional strength training and cooldown workouts in watchOS 7
Safety features
Safety features	Hard-fall detection can call emergency services after immobility and notify emergency contacts; Emergency SOS	Fall detection and Emergency SOS; international emergency calling on cellular versions in supported regions
Battery and connections
Battery life (maker's claim)
Battery life (maker's claim)	Up to 18 hours	Up to 18 hours
Mobile data option
Mobile data option	Yes	Yes
Works with
Works with	iPhone	iPhone
Chip
Chip	S4	S6
Storage
Storage	16 GB	32 GB (better)
Battery life detail
Battery life detail	Built-in rechargeable lithium-ion battery	Built-in rechargeable lithium-ion battery
Charging
Charging	Magnetic charging cable and USB power adapter	1 m magnetic charging cable; full charge in under 1.5 hours, according to Apple's launch announcement
Connectivity
Connectivity	W3 wireless chip; Wi-Fi 802.11b/g/n at 2.4GHz; Bluetooth 5.0; cellular versions add LTE and UMTS with a compatible plan; GPS requires iPhone 5s, cellular iPhone 6, both with iOS 12 at launch	W3 wireless chip and U1 Ultra Wideband chip; Wi-Fi 802.11b/g/n at 2.4GHz and 5GHz; Bluetooth 5.0; cellular versions add LTE and UMTS; requires iPhone 6s or later with iOS 14 at launch
Design
Weight (lightest version)
Weight (lightest version)	30.1 g (better)	30.5 g
Software
Software	watchOS	watchOS
Case materials
Case materials	Aluminium or stainless steel case; ceramic and sapphire crystal back; water resistance under ISO 22810:2010 for shallow-water swimming	Aluminium, stainless steel or titanium; ceramic and sapphire crystal back; 50 m rating under ISO 22810:2010 for shallow-water swimming
Size
Size	40mm 40 x 34 x 10.7 mm, 30.1 g aluminium or 39.8 g steel; 44mm 44 x 38 x 10.7 mm, 36.7 g aluminium or 47.9 g steel; weights exclude bands	40mm 40 x 34 x 10.7 mm, aluminium 30.5 g, steel 39.7 g or titanium 34.6 g; 44mm 44 x 38 x 10.7 mm, aluminium 36.5 g, steel 47.1 g or titanium 41.3 g; case weights exclude bands
Bands
Bands	Compatible with earlier Apple Watch bands of the corresponding size; Nike+ includes Nike bands and watch faces; Hermès includes leather bands and exclusive faces. Nike+ became available 5 October 2018	Apple Watch Studio offers case and band choices; Solo Loop and Braided Solo Loop introduced with Series 6; Nike and Hermès bands and faces also offered
Colours
Colours	Silver, Space Grey and Gold aluminium; Silver, Space Black (DLC) and Gold (PVD) stainless steel; Nike+ Silver or Space Grey; Hermès polished stainless steel	Silver, Space Grey, Gold, Blue or (PRODUCT)RED aluminium; Silver, Graphite or Gold stainless steel; natural or Space Black (DLC) titanium; Nike Silver or Space Grey; Hermès steel or Space Black steel
In the box
In the box	Watch and band, magnetic charging cable and USB power adapter	Watch, band or loop and 1 m magnetic charging cable; no USB power adapter