The Apple Watch Series 4 was officially released to the public on September 21, 2018. This launch marked one of the most significant shifts in the history of wearable technology, moving the Apple Watch from being a luxury iPhone accessory to a legitimate medical-grade health tool. For users and tech enthusiasts tracking the progression of the world’s most popular watch, the arrival of the Series 4 represented a "coming of age" moment for the platform.

The Complete Launch Timeline of Apple Watch Series 4

Understanding the release of a flagship Apple product involves looking at the entire window of its introduction. The Apple Watch Series 4 followed a meticulously planned rollout strategy typical of the Cupertino-based tech giant.

Official Announcement

On September 12, 2018, Apple held its annual "Gather Round" event at the Steve Jobs Theater in Apple Park. While the event also introduced the iPhone XS, iPhone XS Max, and iPhone XR, the Apple Watch Series 4 was the star of the opening segment. It was presented as a fundamental "redesign and re-engineering" of the watch.

Pre-order Window

Following the announcement, Apple opened pre-orders for the Series 4 on Friday, September 14, 2018. This allowed early adopters to secure the new 40mm and 44mm sizes, which were a departure from the previous generation's sizing standards.

Retail Availability

The global release date, when the Apple Watch Series 4 hit store shelves and began arriving at customers' doorsteps, was Friday, September 21, 2018. The initial launch included major markets such as the United States, United Kingdom, Canada, Australia, China, Germany, Japan, and several others.

Discontinuation and Legacy

Interestingly, the Apple Watch Series 4 had a relatively short primary lifecycle. It was discontinued on September 10, 2019, to make way for the Apple Watch Series 5. Despite being sold officially for less than a year, its impact on the design language of subsequent models—stretching all the way to the Series 9 and beyond—cannot be overstated.

Why the Apple Watch Series 4 Design Was a Breakthrough

Before the Series 4, the Apple Watch had maintained the same chassis design for three generations (Series 0 through Series 3). The 2018 release changed everything by introducing a thinner case and a much larger display.

The Shift to 40mm and 44mm

One of the most immediate changes noticed upon the release date was the physical footprint. Apple replaced the 38mm and 42mm case sizes with 40mm and 44mm options. While the cases themselves weren't drastically larger in total volume, the way they utilized space was revolutionary.

The corners of the display were now curved to match the radius of the watch case, a technical feat that required a new type of display technology. This resulted in a screen that was over 30 percent larger than the Series 3. In practice, this meant that text became easier to read, buttons were easier to tap, and complications could offer much more information at a glance.

The LTPO Display Technology

The Series 4 was the first to utilize LTPO (Low-Temperature Polycrystalline Oxide) OLED technology. While the "Always-On" feature wouldn't arrive until the Series 5, the LTPO backplane in the Series 4 was the essential foundation that allowed Apple to manage power efficiency while driving a much larger, higher-resolution screen. In our testing of the device during its peak years, the vibrancy and black levels of this display set a new industry standard that competitors struggled to match for years.

The Health Revolution: ECG and Fall Detection

Perhaps more important than the physical release date was the regulatory "release" of the Apple Watch as a health device. The Series 4 was the first consumer wearable to offer an over-the-counter Electrocardiogram (ECG) feature.

The Electrical Heart Sensor

Built into the Digital Crown and the back crystal of the Series 4 was a set of electrodes. By placing a finger on the Digital Crown for 30 seconds, a user could complete a circuit that allowed the watch to generate an ECG waveform. This was not just a software gimmick; it received De Novo classification from the FDA, meaning it was recognized as a valid way for consumers to detect signs of Atrial Fibrillation (AFib).

From a user experience perspective, this changed the psychology of wearing the watch. It was no longer just about tracking steps or closing "Activity Rings"; it was about proactive heart health. In the months following the September release, countless stories emerged of the Series 4 identifying heart conditions that users were previously unaware of.

Advanced Fall Detection

Another landmark feature introduced with the Series 4 was Fall Detection. This utilized a next-generation accelerometer and gyroscope capable of measuring up to 32 g-forces. The device was programmed to identify the specific trajectory and impact of a "hard fall."

If a user remained immobile for 60 seconds after a detected fall, the watch would automatically call emergency services and send the user's location to their emergency contacts. This feature specifically targeted an older demographic, expanding the Apple Watch's market reach beyond fitness enthusiasts to the "silver economy" and people with specific medical vulnerabilities.

Internal Hardware: The Power of the S4 Chip

When the Series 4 was released, it didn't just look better; it was significantly more powerful. The jump from the Series 3 to the Series 4 felt like moving from a stuttering prototype to a fluid, finished product.

The 64-bit Dual-Core S4 SiP

The S4 System-in-Package (SiP) was a 64-bit processor that Apple claimed was up to twice as fast as the S3. In real-world usage, this was most apparent in the speed at which apps launched and the responsiveness of Siri. The 64-bit architecture was a crucial step in ensuring the watch could handle the more complex algorithms required for real-time health monitoring and the advanced complications of the new Infograph watch faces.

Re-engineered Audio and Haptics

Apple also focused on the "Watch" as a communication device. The speaker was redesigned to be 50 percent louder, making phone calls and Walkie-Talkie interactions much clearer. To prevent echo during calls, the microphone was moved to the opposite side, away from the speaker.

The Digital Crown also received a massive haptic upgrade. Instead of spinning freely with no tactile feedback, the Series 4 used the Taptic Engine to simulate the feeling of mechanical clicks. This made scrolling through lists or zooming into photos feel much more precise and high-end.

Software Synergy with watchOS 5

The release of the Apple Watch Series 4 coincided with the launch of watchOS 5. While the software was available for older models, it was clearly optimized for the Series 4's larger display and faster processor.

The Infograph Face

The Infograph face became the hallmark of the Series 4. With the ability to hold up to eight complications, it allowed users to see weather, heart rate, calendar events, and fitness goals all on one screen. For the first time, users didn't have to swipe between faces to get their essential data. The curved corners of the screen were utilized to show "corner complications" that wrapped around the edges, a design choice that defined the "Series 4 look."

Walkie-Talkie and Podcasts

WatchOS 5 introduced the Walkie-Talkie app, which used FaceTime Audio to allow instant voice communication between Apple Watch users. It also brought the Apple Podcasts app to the wrist for the first time, allowing users to sync their favorite shows and listen via Bluetooth headphones without needing their iPhone nearby.

Comparing the Series 4 to Its Predecessor and Successor

To understand the value of the Series 4 release date, we must look at where it sat in the lineage of Apple wearables.

Series 3 vs. Series 4

The Series 3 was a solid device that introduced LTE, but it felt "chunky" with its small, rectangular screen and thick bezels. The Series 4 made the Series 3 look immediately obsolete. The difference in thickness (the Series 4 was slightly thinner) and the massive increase in screen real estate made the upgrade one of the most compelling in Apple's history.

Series 4 vs. Series 5

When the Series 5 arrived in 2019, many Series 4 owners felt little need to upgrade. The Series 5's primary new feature was the Always-On display. Beyond that, the processor, sensors, and overall design remained almost identical to the Series 4. This speaks to how "ahead of its time" the Series 4 was at its 2018 launch. It was a "leap" year for Apple, whereas the Series 5 was an "evolutionary" year.

Materials and Pricing at Launch

Apple maintained its strategy of offering various materials to hit different price points and style preferences.

  • Aluminum Models: These were the most popular and started at $399 for the 40mm GPS model and $499 for the GPS + Cellular model. They were available in Silver, Space Gray, and a revamped Gold finish.
  • Stainless Steel Models: These were positioned as the premium "Apple Watch" collection, starting at $699. They featured sapphire crystal displays and were available in Silver, Space Black, and a new, stunning Gold Stainless Steel that matched the iPhone XS.
  • Special Editions: The Nike+ and Hermès versions also returned. The Nike+ version included exclusive bands and watch faces, while the Hermès version remained the pinnacle of luxury with handcrafted leather bands.

The Long-Term Support and Reliability

The longevity of the Apple Watch Series 4 is one of its most impressive traits. While most tech products begin to feel sluggish after three years, the Series 4 remained a viable daily driver for many years. It supported software updates all the way through watchOS 10, meaning a user who bought the device on its 2018 release date received five years of major feature updates.

This durability was due to the headroom provided by the S4 chip. Apple had over-engineered the processor for 2018, which paid dividends in 2021 and 2022 as the watch continued to run modern apps without significant lag.

How to Check if Your Apple Watch is a Series 4

Since the Series 4 looks very similar to the Series 5 and Series 6, many users often get confused about which model they own. To verify if you have the 2018 model:

  1. Check the Back Crystal: Flip the watch over. The text etched around the heart rate sensor will explicitly say "Series 4," along with the case size (40mm or 44mm) and material (e.g., Aluminum or Stainless Steel).
  2. Check the Settings: On the watch, go to Settings > General > About. Look for the Model number and cross-reference it with Apple's official database.
  3. Physical Cues: Unlike the Series 3, the Series 4 has a black ceramic and sapphire crystal back on all models. It also lacks the "Red Ring" on the Digital Crown found on Series 3 cellular models; instead, it has a more subtle "Red Circle" outline.

Frequently Asked Questions (FAQ)

What was the exact release date for the Apple Watch Series 4?

The Apple Watch Series 4 was released in retail stores and to customers on September 21, 2018.

Can the Apple Watch Series 4 run the latest watchOS?

The Apple Watch Series 4 is compatible with watchOS 10, which was released in 2023. However, it does not support watchOS 11, marking the end of its official major software update cycle.

What is the difference between the 40mm and 44mm Series 4?

The only differences are the physical size of the case, the size of the display, and the battery capacity. The 44mm version has a slightly larger battery and more screen area, while the 40mm version is designed for smaller wrists. The internal processor and health sensors are identical in both.

Does the Apple Watch Series 4 have an Always-On display?

No. The Always-On display was introduced with the Apple Watch Series 5 in 2019. The Series 4 screen remains dark until you lift your wrist or tap the display.

Is the ECG feature available in all countries?

No, the ECG feature requires regulatory approval in each country. While it was available in the US at launch (via a software update shortly after), it rolled out to other regions over the following months and years as local health authorities granted clearance.

Was the Series 4 waterproof?

The Apple Watch Series 4 is water-resistant to 50 meters under ISO standard 22810:2010. This means it can be used for shallow-water activities like swimming in a pool or ocean. It is not suitable for scuba diving or high-velocity water sports.

Summary of the Series 4 Impact

The Apple Watch Series 4 release date of September 21, 2018, was a turning point for the industry. By introducing a larger, more beautiful display and life-saving health features like ECG and Fall Detection, Apple moved the smartwatch from a "nice-to-have" gadget to an essential health companion.

Even years after its discontinuation, the Series 4 remains the blueprint for the modern Apple Watch. Its design language—the rounded corners, the 40/44mm sizing, and the sensor-packed ceramic back—continues to influence the lineup today. For those who owned it, the Series 4 wasn't just a watch; it was the first time a computer on the wrist felt truly personal and profoundly capable of protecting the person wearing it.