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The Apple Watch Series 4 still handles basic smartwatch jobs, but it is no longer a sensible default buy in 2026. Notifications, workouts, GPS, Apple Pay, heart-rate tracking, Fall Detection and ECG remain useful on a working unit. The problem is age: Apple lists Series 4’s software ceiling as watchOS 10.6.1, classifies the models as vintage or, for some variants, obsolete, and does not guarantee that the legacy iPhone requirement will work with every current iPhone. Buy one only if it is exceptionally cheap, returnable and demonstrably healthy. If you already own one, keep using it if it pairs and its battery meets your needs.
This is a retrospective on the Series 4, introduced in 2018, with a buying verdict updated for 2026—not a claim that it remains current.
Apple Watch Series 4 at a glance
| Specification | Apple Watch Series 4 |
|---|---|
| Generation | 2018 |
| Case sizes | 40mm and 44mm |
| Display | LTPO OLED Retina, up to 1,000 nits; no always-on display |
| Processor | S4 64-bit dual-core |
| Storage | 16GB |
| GPS | GPS, GLONASS, Galileo and QZSS |
| Cellular | Optional LTE/UMTS on cellular models |
| Water resistance | 50 meters under ISO 22810:2010, subject to Apple’s activity limits and the condition of the individual watch |
| Original battery estimate | Up to 18 hours in Apple’s 2018 testing; not a realistic promise for an aged used battery |
| Maximum listed software branch | watchOS 10.6.1 |
| ECG | Supported where regional, regulatory, software and user requirements are met |
Apple’s Series 4 specifications and compatibility table are the reference for these figures.
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Why Series 4 mattered—and what that means now
At launch, Series 4 was a substantial redesign rather than a minor refresh. It replaced the earlier 38mm and 42mm sizes with 40mm and 44mm cases, used a larger display area, and introduced the S4 chip, which Apple advertised as up to twice as fast as the prior generation. It also brought an electrical heart sensor for ECG, Fall Detection, a stronger accelerometer and gyroscope, and 16GB of storage. Optional cellular models added LTE and UMTS.
#1 Best Overall
- 📞 【Bluetooth 5.3 Calls & Smart Notifications】 Make and answer calls directly from your smartwatch with stable Bluetooth 5.3 connectivity. Receive vibration alerts for calls and messages from Facebook, WhatsApp, Instagram, Twitter and more.
- ⌚ 【1.96 HD Touch Screen & 200+ Watch Faces】 Enjoy a large 1.96 HD full-touch display with smooth operation and clear visuals. Choose from 200+ watch faces in the GloryFit app or customize the screen with your favorite photo.
- 💖 【24/7 Health Monitoring】 Track heart rate, blood oxygen, stress, sleep and daily activity with built-in sensors. View your health and activity data in the GloryFit app to better understand your daily wellness.
- 🏊 【110+ Sports Modes & IP68 Waterproof】 Supports 110+ sports modes including running, walking, hiking, cycling, basketball and fitness. Tracks steps, calories, distance and heart rate during workouts. IP68 waterproof for daily exercise, sweat and hand washing.
- 🚀 【7-Day Battery & Multiple Smart Features】 Enjoy up to 7 days of use and about 30 days of standby after a 2-hour charge. Includes alarm, timer, stopwatch, music control, weather, camera control, calculator, sedentary reminder and more. Compatible with Android and iPhone.
Those were important improvements in 2018. They do not make the watch equivalent to a current Apple Watch: the screen is not always on, its software stops at watchOS 10.6.1, and later health, safety and interaction features are absent.
Design, size and display
The 40mm model has a 324 × 394-pixel display with 759 square millimeters of display area; the 44mm version has 368 × 448 pixels and 977 square millimeters. Both use an LTPO OLED Retina display rated up to 1,000 nits. The case is 10.7mm deep. Aluminum models have Ion-X glass, while stainless-steel models have sapphire crystal over the display; the rear uses ceramic and sapphire crystal. Aluminum case weights are 30.1g for 40mm and 36.7g for 44mm, excluding the band. See Apple’s model identification and specifications.
For notifications, workout metrics, timers and Apple Pay, the display remains spacious and readable. The more noticeable limitation is interaction: the display goes dark when not in use, unlike the always-on displays available on later models. Choose 44mm if larger text and workout figures matter; 40mm is lighter and often a better fit on smaller wrists. For a used watch, condition and battery health matter more than the size difference.
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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteSeries 4 came in aluminum and stainless steel, with Nike and Hermès editions among the variants. A special edition does not change the central buying calculation: software support and serviceability are still constrained by the age of the hardware.
Everyday performance and apps
The S4 was a significant speed improvement for its time. A healthy unit can still be useful for notifications, timers, workouts, music controls, Apple Pay and simple watch apps. There is no basis to assume that every aged Series 4 will feel equally responsive: battery condition, installed software and the particular app all affect the experience.
The bigger long-term issue is software. Series 4 cannot install watchOS versions after 10.6.1, so it does not get watchOS 11, watchOS 26 or features introduced in later releases. Third-party app support is also less predictable when developers require newer watchOS versions. “It turns on” is not the same as being a good long-term smartwatch purchase.
Rank #2
- No APP & Phone Required Fitness Tracker Watch: This Fitness Tracker watch doesn't require any App or smartphone connections! It's as simple to use as a regular watch but smarter. Perfect for anyone looking for an easy fitness tracker without the hassle of smartphone setups.
- Heart Rate and Sleep Monitoring: The Fitness Tracker monitors your heart rate automatically all day, and you can select manual mode through the App. The fitness Watch also monitors your sleep at night, providing a detailed analysis of your sleep quality (deep sleep, light sleep, awake time). It is a health advisor for women men in daily life.
- Multi Sport Modes with Activity Tracking: The fitness tracker features 9 sport modes like running, walking and more. Additionally, the activity tracker records daily steps, calories burned, walking distance and active time throughout the day. You can also set a daily steps goals through the App to track your progress.
- Smart Notification Reminder: You can get SMS messages, and SNS notifications directly on your wrist including Facebook, Twitter, Gmail ect. You won't miss any important calls and message and stay updated. Please note: the smart watch can not make calls or text.
- Long Battery Life and IP68 Waterproof: This smart watch only requires 2 hours of charging and can be used for 5-7 days continuously, IP68 waterproof rating can withstand daily sweat, washing hands and rainy day, allowing you to fully enjoy your workouts.
Health and fitness: what still works
Series 4 has optical heart-rate monitoring, an electrical heart sensor and the ECG app, alongside Activity rings, workout tracking, GPS and a barometric altimeter for elevation data. Irregular-heart-rhythm notifications and Fall Detection may also be available, depending on software, region, setup and service availability. ECG is listed for Series 4 and later, excluding SE models, in Apple’s comparison information.
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsThese features can make an inexpensive Series 4 useful for basic activity tracking or for someone who specifically wants ECG capability. They are not a substitute for newer hardware. Series 4 lacks later-generation capabilities such as blood oxygen functionality, sleep-apnea notifications, the Vitals app, wrist-temperature sensing, newer cycle-tracking capabilities, hypertension notifications and Crash Detection. Exact availability of newer features varies by model, region and software; Apple’s model comparison shows the distinction.
ECG is not a diagnosis. The app’s availability depends on geography and regulatory approval as well as setup and device requirements. A reading cannot detect every heart condition, and a normal result does not rule out a medical emergency. Discuss results with a qualified medical professional. Seek care for concerning symptoms rather than relying on the watch.
Battery life is the key used-buying risk
Apple’s “up to 18 hours” figure was based on testing with preproduction Series 4 units in August 2018. It describes an original test condition, not what a many-years-old battery should deliver today. Actual runtime depends on battery age, notifications, workouts, GPS, cellular use and software state.
Ask whether the watch reliably lasts through your normal day. If you want overnight sleep tracking, check that it can make it through the night and still have enough charge for the morning. Watch for unexpected shutdowns, rapid drain, inconsistent charging, or a screen lifting from the case. A raised display or visible gap can indicate battery swelling: do not charge or wear that watch; return it or have it handled by a qualified service provider.
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Rank #3
- 【Crystal-Clear Communication】AEAC smartwatch delivers clear call quality with high-definition speakers and microphones. Built with an AI assistant, it enables smooth voice commands and hands-free calls.
- 【Comprehensive Health Monitoring】The AEAC smartwatch tracks vital health metrics—blood oxygen, heart rate, stress, and sleep analysis—providing you with valuable insights for enhanced well-being.
- 【Long-Lasting Battery】Enjoy up to 10 days of use on a quick 2-hour charge. Will monitor your heart rate, steps, activity routes, and calorie burn around the clock, offering a complete view of your health and fitness.
- 【110+ Sports Modes & Waterproof】With 110+ sports modes, this fitness watch supports a wide range of activities, from yoga to swimming. Its 3ATM water-resistant design ensures reliable performance in wet conditions.
- 【1.32" AMOLED Touchscreen】 Features a 1.32-inch AMOLED display for sharp visuals and smooth responsiveness. The watch face measures 43 mm, offering a clear and comfortable viewing area. Choose from 200+ watch faces or personalize with your own photos, making the watch uniquely yours
Repair economics are another concern. Apple lists Series 4 as vintage, with service dependent on parts availability; some Series 4 variants are obsolete. Apple says service for obsolete products is discontinued. Do not assume Apple will perform a conventional battery replacement or that a service option will be inexpensive. Check Apple’s vintage and obsolete product policy for the exact model and region before paying for service.
Software and iPhone compatibility
Apple’s compatibility table lists Series 4 with an iPhone 6 or later running iOS 12 or later, and lists watchOS 10.6.1 as its maximum branch. Those are legacy minimum requirements, not a promise that Series 4 will pair with every iPhone or iOS release available in 2026. The watch cannot be updated to a newer watchOS branch to resolve a future compatibility mismatch.
If you use a current iPhone, confirm that the exact watchOS installed on the watch can pair with the iOS version on your phone before buying. Do not rely only on an old compatibility line or the seller saying that it worked with their phone. Ideally, pair the watch to your own iPhone during the return window. If pairing fails, or the seller cannot demonstrate setup after erasing it, do not treat that as a small inconvenience: it may make the watch unusable for you.
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1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteThe software cap also means no new watchOS features after the final supported branch, and lower confidence in future app and security compatibility. Apple’s page documents the supported range; it does not promise a particular number of future security updates.
Water resistance on an eight-year-old watch
Series 4 was rated water resistant to 50 meters under ISO 22810:2010, for shallow-water activities such as pool or ocean swimming. Apple excludes scuba diving, waterskiing and activities involving high-velocity water or deep submersion. That original rating is not a guarantee for a secondhand example: impact, cracks, repairs, aging seals and adhesive deterioration can compromise resistance.
Do not buy an old Series 4 on the assumption that it is safe to swim with, especially if it has been opened, repaired, dropped or damaged. Avoid scuba diving, high-speed water sports and sauna or steam-room use. Never treat a cracked or questionable device as waterproof.
Rank #4
- 【Superb Visual Experience & Effortless Operation】Diving into the latest 1.58'' ultra high resolution display technology, every interaction on the fitness watch is a visual delight with vibrant colors and crisp clarity. Its always on display clock makes the time conveniently visible. Experience convenience like never before with the intuitive full touch controls and the side button, switch between apps, and customize settings with seamless precision.
- 【Comprehensive 24/7 Health Monitoring】The fitness watches for women and men packs 24/7 heart rate, 24/7 blood pressure and blood oxygen monitors. You could check those real-time health metrics anytime, anywhere on your wrist and view the data record in the App. The heart rate monitor watch also tracks different sleep stages for light and deep sleep,and the time when you wake up, helps you to get a better understanding of your sleep quality.
- 【120+ exercise modes & All-Day Activity Tracking】There are more than 120 exercise modes available in the activity trackers and smartwatches, covering almost all daily sports activities you can imagine, gives you new ways to train and advanced metrics for more information about your workout performance. The all-day activity tracking feature monitors your steps, distance, and calories burned all the day, so you can see how much progress you've made towards your fitness goals.
- 【Messages & Incoming Calls Notification】With this smart watch fitness trackers for iPhone and android phones, you can receive notifications for incoming calls and read messages directly from your wrist without taking out your phone. Never miss a beat, stay in touch with loved ones, and stay informed of important updates wherever you are.
- 【Essential Assistant for Daily Life】The fitness watches for women and men provide you with more features including drinking water and sedentary reminder, women's menstrual period reminder, breath training, real-time weather display, remote camera shooting, music control,timer, stopwatch, finding phone, alarm clock, making it a considerate life assistant. With the GPS connectivity, you could get a map of your workout route in the app for outdoor activity by connecting to your phone GPS.
GPS, cellular and model variations
Series 4 was sold as GPS aluminum, GPS + Cellular aluminum, and GPS + Cellular stainless steel models, along with special editions. A GPS model generally depends on the paired iPhone for calls, messages, streaming and many connected features. A cellular model can operate more independently when activated, but cellular service requires a compatible carrier plan and support for that exact model. Bands and carrier support can vary by region, so a cellular watch that worked for its previous owner may not activate for you. Verify the model number and carrier compatibility before purchase; do not pay extra for cellular capability you cannot use.
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Apple’s magnetic charging system means a compatible charger is essential. Confirm that the listing includes a working magnetic charging cable—not just a stand—and test that the connection is consistent. Also confirm the case size and band fit; do not assume every band listing is interchangeable without checking the connector and size.
Used Series 4 buying checklist
Before you pay
Ask for clear photos or a video showing:
- The display both off and on, so you can look for cracks, bright spots, dead areas or ghost touches.
- The rear sensors and charging surface.
- The exact model number, watchOS version and Battery Health screen.
- The watch powering on and charging with the included charger.
- The setup or pairing screen after erasure, and confirmation that Activation Lock is removed.
- Cellular status and model details if cellular service matters to you.
Prefer a seller with a real return window or meaningful buyer protection. A box does not prove authenticity, battery health or good condition.
Test it at pickup or as soon as it arrives
- Confirm setup: pair it with your own iPhone, and make sure the previous owner has removed the watch from their Apple Account. Erasing a watch alone does not necessarily remove Activation Lock.
- Inspect the hardware: test the Digital Crown, side button, touchscreen, speaker, microphone and haptics. Check the display edges and rear crystal for impact damage or separation.
- Check charging and battery: confirm the charger connects consistently, inspect Battery Health where available, and observe real-world drain during your return period.
- Test core functions: start an outdoor workout to check GPS lock, verify that heart-rate readings appear during a workout, and confirm notifications and Apple Pay if you plan to use them.
- Check ECG expectations: if ECG is your reason for buying, verify availability and setup in your country and account. An absent app does not by itself prove the watch is counterfeit; regional, regulatory, software, account, age and hardware factors can matter.
- Verify cellular separately: have the intended carrier confirm that the exact model can be activated before paying a premium for cellular.
Return or reject the watch if Activation Lock remains, it cannot pair with your iPhone, its battery drains dramatically, the display is cracked or lifting, or cellular activation is essential but unverified. If the seller refuses a return, the price must be low enough to compensate for the risk—and a cheap price does not make a locked watch usable.
Which buyer should consider Series 4?
- You already own one: Keep using it if it pairs with your iPhone, works reliably and its battery meets your routine. Upgrade when software limitations, battery life or missing features become a problem.
- You are receiving one for free: It can be a worthwhile basic watch if it is not Activation Locked and works with your iPhone. Check condition before relying on it for swimming or overnight tracking.
- You want to buy used: Only consider it at a very low price, with a healthy battery, confirmed pairing and a return option. Compare the total cost with a newer used or refurbished watch; no universal price ceiling is reliable without current local listings.
- You want several years of support: Pass. The watchOS ceiling and vintage service status make Series 4 a poor bet for a long ownership horizon.
- You want ECG at the lowest cost: Series 4 has ECG where supported, but consider a newer non-SE Series model if the price difference is reasonable. It is a safer path to newer software and hardware.
- You mainly want an inexpensive current Apple Watch: Look at a current SE model if ECG is not required.
Series 4 versus newer Apple Watches
| Alternative | Best for | Why it is a better 2026 purchase | Trade-off |
|---|---|---|---|
| Apple Watch SE 3 | Lower-cost current Apple Watch basics | Newer hardware and current software compatibility; buying new also avoids inheriting an old battery | It does not offer ECG or all of the higher-end health features |
| Apple Watch Series 10 | A modern mainstream watch, including through refurbished or discounted stock | Newer display and health capabilities, faster charging and a longer support runway | Not the newest standard model, and local refurbished pricing and availability vary |
| Apple Watch Series 11 | Buyers prioritizing the current mainstream model and longevity | Current software and newer health and connectivity features; new-device warranty when bought through Apple or an authorized seller | Costs more than an old Series 4 and may be unnecessary for basic notifications |
| Apple Watch Ultra 3 | Endurance, outdoor and rugged-use needs | Designed for buyers who need its larger battery, rugged construction or specialized outdoor features | Much larger, heavier and more expensive than needed for ordinary notifications and casual fitness |
Apple’s SE and Series 4 comparison and Series 10 comparison show how far the lineup has moved. For Series 11 and Ultra 3, check Apple’s current Watch page and local availability. Prices and stock vary, so compare the actual price, warranty, return terms and battery disclosure available where you live rather than assuming one model is always the best value.
Final verdict
Series 4 was a landmark Apple Watch, and a healthy one can still cover everyday smartwatch basics. In 2026, however, its software ceiling, uncertain pairing with current iPhones, aged batteries and vintage/obsolete service status outweigh the appeal of a low sticker price for most buyers. Keep one that already works. Accept a free one after checking it. For a purchase, choose Series 4 only if it is exceptionally cheap, returnable and compatible with your iPhone; otherwise, a newer used or refurbished model—or a current SE if ECG is not essential—is the safer choice.
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