I have an Your current Apple WatchApple Watch Series 12Apple Watch Ultra 4Apple Watch Series 11Apple Watch SE 3Apple Watch Ultra 3Apple Watch Series 10Apple Watch Series 9Apple Watch Ultra 2Apple Watch Series 8Apple Watch SE (2nd generation)Apple Watch UltraApple Watch Series 7Apple Watch SE (1st generation)Apple Watch Series 6Apple Watch Series 5Apple Watch Series 4Apple Watch Series 3Apple Watch Series 1Apple Watch Series 2Apple Watch (1st generation)Apple Watch Series 8▾
and I'm looking at the The Apple Watch you are consideringApple Watch Series 12Apple Watch Ultra 4Apple Watch Series 11Apple Watch SE 3Apple Watch Ultra 3Apple Watch Series 10Apple Watch Series 9Apple Watch Ultra 2Apple Watch Series 8Apple Watch SE (2nd generation)Apple Watch UltraApple Watch Series 7Apple Watch SE (1st generation)Apple Watch Series 6Apple Watch Series 5Apple Watch Series 4Apple Watch Series 3Apple Watch Series 1Apple Watch Series 2Apple Watch (1st generation)Apple Watch SE 3▾

watchOS is the software that runs Apple Watch: the watch faces, the built-in apps and the settings. A new version can bring redesigned apps, new watch faces and new workout features.

To install a new watchOS, the paired iPhone needs a matching iOS: watchOS 27 needs iPhone 11 or later, or iPhone SE (2nd generation or later), with iOS 27. If the watch cannot run the newest version, Software Update offers the newest one it can use. After watchOS 11 came watchOS 26, so watchOS 11 to watchOS 27 is two updates, not sixteen.

Matters most if: You are buying a used Apple Watch, or your iPhone is too old for the latest iOS.

The most recent update Apple has released for the newest watchOS version this Apple Watch can run, and the day it came out, from Apple's list of security releases.

Apple's list says which updates fixed security problems. A maintenance update fixed other things and lists no security fixes. Apple says not all known security issues are fixed in older watchOS versions, even ones that still get updates.

Matters most if: You are buying a used Apple Watch, or you use Apple Pay on it.

The chip is the watch's brain. Apple names its watch chips S1, S2 and so on; the newest is the S11.

The chip decides which features a watch can get. Double tap and on-device Siri arrived with the S9 chip in Series 9 and Ultra 2: double tap uses the chip's Neural Engine, which Apple says processes machine learning tasks. Apple said the S6 chip in Series 6 let apps launch 20 percent faster.

The space on the watch for apps, music, podcasts, audiobooks and photos. GB means gigabytes. Apple Watch models have from 8 GB to 64 GB.

Storage matters most if you keep music, podcasts or audiobooks on the watch to play when your iPhone is not with you. On Series 3, the GPS + Cellular version has 16 GB and the GPS version 8 GB.

Matters most if: You want to listen to music or podcasts on runs or walks without your iPhone.

Tap the index finger and thumb of the hand wearing the watch together twice. The watch treats it like pressing the main button on the screen, so you can control it with one hand.

Answer or end a call, stop a timer, play or pause music, snooze an alarm, or scroll through the Smart Stack of widgets. It does not work in Low Power Mode, during Sleep Focus, when your wrist is down or when the watch is locked.

Matters most if: Your other hand is often busy.

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The watch can handle some Siri requests on the watch itself.

Apple says requests that need no information from the internet, such as starting a workout or setting a timer, work without Wi-Fi or cellular, and the answers come quicker. Apple added it with Series 9 and Ultra 2.

Matters most if: You use Siri for timers and workouts, or you often go out without your iPhone.

The price Apple charged in the US on launch day for the cheapest version, before tax.

This is not what it costs today. Older models drop in price over time, so check the used and refurbished links for current prices.

The optical heart sensor on the back of the watch flashes green lights against your wrist. Blood absorbs green light and more blood flows with each heartbeat, so the watch can count your heart rate in beats per minute (BPM).

The Heart Rate app shows your heart rate at rest, while walking and during and after a workout, and you can turn on alerts for a heart rate that stays above or below a level you choose. We show Apple's name for the sensor; Apple's tech specs do not say what changed between generations. Series 12 and Ultra 4 have what Apple calls the Health Sensing System, which measures heart rate as often as every 5 seconds during the day.

Matters most if: You train by heart rate, or want an alert when your heart rate stays above or below a level you set.

ECG stands for electrocardiogram: a recording of the electrical signals that make your heart beat. The ECG app records one in 30 seconds while you hold a finger on the Digital Crown.

The app checks the recording for atrial fibrillation (AFib), a form of irregular heart rhythm, and saves it in the Health app, where you can export a PDF for your doctor. Apple says the app cannot detect a heart attack, blood clots or a stroke, and is not intended for people under 22. No Apple Watch SE model has it.

Matters most if: You want to record your heart rhythm on the spot, for example when you feel a rapid or skipped heartbeat.

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Blood oxygen is the percentage of oxygen your red blood cells carry from your lungs to the rest of your body. The Blood Oxygen app measures it with a red light against your wrist; a reading takes 15 seconds while you keep your arm still.

With background measurements on, the watch also measures now and then, usually when you are not moving. Apple says the readings are not intended for medical use and are only for general fitness and wellness, and the app is for people 18 and older. No Apple Watch SE model has it.

Matters most if: You want to follow your blood oxygen overnight or at high elevation.

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Apple describes sleep apnea as a potentially serious condition where breathing stops repeatedly during sleep. The watch uses its motion sensor to pick up small wrist movements linked to interruptions in normal breathing.

Wear the watch to bed. If nights with more breathing disturbances become frequent over 30 days, you get a notification of possible sleep apnea, with a PDF to discuss with your healthcare provider. Apple says it is not intended for people already diagnosed with sleep apnea or under 18.

How many hours the watch lasts on a full charge with Low Power Mode on, in Apple's own test. Low Power Mode saves battery by turning some features off.

It turns off the Always-On display, background heart rate and blood oxygen readings, and gestures like double tap. Apple says other notifications may be delayed and emergency alerts may not arrive. Workouts still measure heart rate and pace.

Matters most if: You travel or camp and cannot charge every night.

The case size in millimeters (mm), measured from the top to the bottom of the case; 10 mm is about 0.4 inch. Most models come in two sizes; Ultra models come in one, 49 mm.

The larger size has a larger screen and weighs a little more. Bands come in sizes too: before you buy one, check that it fits your case size.

Matters most if: You want the largest screen for reading, or the lightest watch to wear all day and night.

What the case is made of: aluminum, stainless steel, titanium or ceramic depending on the model, or 18-karat gold on the first Apple Watch Edition.

Aluminum is the lightest. Where Apple lists the front glass, aluminum cases have Ion-X glass (Ceramic Shield 2 on Series 12), and stainless steel, titanium, ceramic and gold cases have sapphire crystal. The colors you can choose also depend on the material.

Matters most if: You want the lightest case, or a sapphire front.

How much the watch case weighs, in grams (g); 28 grams is about 1 ounce. Apple lists a weight for each case size and material, and on some models for the GPS and GPS + Cellular versions.

Comparisons show the lightest to the heaviest case Apple lists; the spec page lists each one. Bigger cases and heavier materials weigh more.

Matters most if: You plan to wear the watch all day and to bed for sleep tracking.

IP6X is a dust-resistance rating under the IEC 60529 standard. Apple Watch Series 7 and later and every Ultra model are rated IP6X.

Apple says the rating makes the watch more durable in places like the beach or the desert. It covers dust only; water resistance is rated separately.

Matters most if: You spend time at the beach, in the desert or on dusty trails.

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Ultra Wideband (UWB) is a short-range wireless technology Apple describes as spatial awareness. Apple's list puts Series 6, 7 and 8 and the first Ultra on the first-generation chip, and Series 9 and later and Ultra 2 and later on the second generation; Apple Watch SE models are not on the list.

With the second-generation chip, the watch can guide you to your iPhone with Precision Finding. With some cars, Apple Watch Series 6 or later can unlock the car as you walk up to it (passive entry). Ultra Wideband availability varies by country or region.

Matters most if: You often misplace your iPhone, or your car works with car keys in Apple Wallet.

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