Archive note: this overview describes Apple Watch Series 6 at its 2020 launch. Feature availability depends on the model, region and software; it is not a current buying recommendation.
Blood Oxygen: A Wellness Feature
Apple Watch Series 6 introduced a Blood Oxygen app intended to give users another view of their general fitness and wellness. The sensor uses four LED clusters and four photodiodes to estimate blood oxygen saturation.
These measurements are not intended for medical diagnosis or treatment. A watch reading cannot establish that a person is healthy, and symptoms should not be dismissed because the reading looks reassuring.
The LEDs shine light onto the wrist, and the photodiodes measure the light reflected back. The watch’s software uses this information to estimate oxygen saturation. The sensor is in the Apple Watch—not the iPhone, as the original wording suggested.
ECG Readings and Their Limits
The ECG app uses electrodes in the Digital Crown and back crystal to record an electrical signal from the heart. It can classify certain recordings, but it does not detect every heart condition and is not a substitute for medical evaluation.
An app result labelled “sinus rhythm” describes the rhythm recorded during that measurement. It is not an all-clear for overall heart health. Apple’s guidance explains the app’s limits and when a result may be inconclusive.
Activity, Sleep and Elevation
Other features include setting sleep goals, tracking activity and viewing workout information. The always-on Retina display makes it easier to check the watch face and metrics without raising the wrist, including outdoors.
An always-on altimeter tracks changes in elevation. Music and podcasts offer another way to use the watch during everyday activity, with availability depending on the app, connection and subscription.
Case Materials and Watch Bands
At launch, Series 6 added blue and red aluminium case options. Apple stated that the aluminium cases used recycled aluminium; that is more specific than describing the entire watch as “100% environmentally friendly.”
The Solo Loop used silicone rubber, while the Braided Solo Loop combined silicone threads with recycled polyester yarn. Both offered alternatives to a conventional clasped watch band.
Staying Connected Without a Nearby Phone
A GPS + Cellular model with a supported mobile plan can make calls, send messages and use connected services when the paired iPhone is not nearby. The watch can also hold supported tickets and boarding passes, provide directions and respond to Siri.
Those features are useful for a walk or outing, but they depend on network coverage, carrier support and configuration. Cellular capability should not be assumed for every Series 6 model.
The Series 6 combined everyday connectivity with fitness and wellness tools. Its appeal was the convenience of having those features on the wrist, while understanding what each measurement could—and could not—tell the wearer.
Sources: Apple’s Series 6 launch announcement, Blood Oxygen guidance and ECG app guidance.