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Apple A-Z » Apple Watch

Apple Watch Series 4

Apple Watch Series 4

The Apple Watch Series 4 signaled a change in design, including a new larger display, a faster processor, and the key addition of ECG monitoring, giving users more information about their heart health.

● 2018 flagship
● Larger edge-to-edge display
● Size increases to 40mm and 44mm
● Faster S4 processor
● Second-generation optical heart sensor
● ECG functionality
● Find great Apple Watch deals
Discounted prices start at $359

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Launched on September 12, 2018, the Apple Watch Series 4 signaled a departure from the design aesthetic of the Apple Watch Series 3 in favor of a larger yet thinner smartwatch, one that provided all the core functionality of the original with some new features. 

The Apple Watch Series 5 replaced it when it launched in 2019. The Apple Watch Series 6 then took the place of the 2019 model upon its arrival in September 2020. The Apple Watch SE now sits in a new mid-ranged spot next to the Apple Watch Series 3, which lives on as a budget option.

Apple Watch Series 4 features

External Design

While sharing the same design language as the Apple Watch Series 3, the Series 4 enhances the concept by opting for larger displays. Still using a square OLED Retina display with Force Touch, the 38mm and 42mm sizes have been upsized to 40mm and 44mm versions. 

Edge-to-edge displayThe Apple Watch Series 4 has a bigger edge-to-edge display

The resolutions are 324 by 394 pixels in the 40mm version and 368 by 448 pixels in the 44mm, with both capable of producing 1,000 nits of brightness. The screen change to an edge-to-edge design also results in a display over 30-percent larger than the previous models while still minimizing the physical impact of offering more screen space. 

The 44mm models are 38mm wide and 44mm high, with a depth of 10.7mm. The 40mm versions are 34mm wide, 40mm high, and again with a depth of 10.7mm. 

Despite the change in size making them slightly larger, bands made for earlier models will continue to fit the Series 4. 

As usual, one side features the Side Button and Digital Crown, used in concert with the taps and swipes of the main display to move through watchOS. Apple refreshed the Crown once again to show a ring instead of a colored dot, with the black version used to denote the GPS model while red signifies the inclusion of cellular connectivity. 

The Digital Crown received a mechanical upgrade and a visual one, with it gaining haptic feedback. 

The speakers were redesigned to be 50% louder for audio, with the microphone moved to the opposite side to minimize echoes.

Around the back is the other big external change for the model, with Apple refining the optical heart sensor to a second-generation version. The sensor fundamentally functions the same way, shining light into the user's wrist to search for a pulse in a technique known as photoplethysmography, but rather than taking the form of four circles, there is instead one main circle with a single central port for light.

Heart rate sensor The new heart rate sensor is one large sensor instead of four smaller ones

In terms of materials and finishes, the Apple Watch Series 4 shipped in aluminum with silver, gold, and space gray finishes for both GPS and Cellular versions, along with a stainless steel option with polished silver, gold, and space black options for Cellular models.

The Apple Watch Edition option was abandoned for a second time, with the previously sold ceramic option not available to purchase for this iteration. Instead, all models of the Series 4 have ceramic backs. 

However, Apple offered Nike+ versions in silver and space gray aluminum, complete with exclusive Sports Bands and Loops, and Apple Watch Hermes in polished stainless steel. Both variants included exclusive watch faces. 


Apple's tradition of improving its products over time continues with the Apple Watch Series 4 using the S4 processor, a 64-bit chip with twice the performance of the S3 used in the previous generation. This lends itself to running apps smoother than before and launching said apps quickly. 

Along with the processor, change is an upgrade to the three-axis gyroscope, with its having twice the dynamic range than previously offered, at up to 32G. Apple also switched over to the W3 wireless chip, enabling Wi-Fi connectivity over 802.11n 2.4GHz networks and Bluetooth 5.0 support.

No changes were made to the storage capacity from the Series 3, with users able to take advantage of 16 gigabytes, enabling some music to be stored. 

Battery life is rated at up to 18 hours of usage, though ultimately, this depends on how users actually employ the wearable device each day. 

Other onboard elements include GPS, GLONASS, Galileo, QZSS support, a barometric altimeter, water resistance to 50 meters, an ambient light sensor, and support for Apple Pay and GymKit.


The biggest feature of the Apple Watch Series 4 is an electrocardiogram function or ECG. The first consumer device available over the counter to offer the feature with U.S. Food and Drug Administration approval, users can use the ECG app on their Apple Watch to quickly check the status of their heart, beyond the pulse. 

Users must complete a circuit by touching the Digital Crown with a finger from the arm that isn't wearing the Apple Watch, with the rear heart monitoring sensor array being the second point of contact. After 30 seconds, the Apple Watch provides a close reading of whether it detects a sinus rhythm, signs of atrial fibrillation (AFib), or an "Inconclusive" result. 

Built-in ECG The built-in ECG function uses the Digital Crown

Regardless of what the Apple Watch advises, the full recording from the reading is offered in the connected iPhone Health app, with the added option to share it with a doctor or other health professional as a PDF. 

Unusually for an announced marquee hardware feature, the ECG app wasn't available at launch, with users having to wait until Apple added support in a later software update. In the United States, the feature was part of watchOS 5.1.2, while other markets had longer waits.

The delays were likely due to Apple having to seek regulatory approval for each market it wanted to offer ECG functionality, with its only becoming available once granted. 

Since its introduction, the ECG function has been credited with potentially saving the lives of many users. Numerous reports have surfaced where users were alerted to signs of atrial fibrillation, prompting a visit to their regular physicians and further medical assistance in some cases. 

Irregular Heart Beat and Fall Detection

A feature introduced at the same time as the ECG but also usable on older Apple Watch models is irregular heart notifications, where the Apple Watch warns if the user's pulse is unusually high or low for 10 minutes or longer.

Fall detection Fall detection can and has saved lives

The extended dynamic range of the accelerometer also enables a function for detecting if the user has fallen over, including slips, trips, and even car accidents. Once a fall is detected, the Apple Watch will attempt to get a response from the user, and if configured to do so, it can be set to alert emergency services and the emergency contact to the event. 

Both the irregular heart notifications and fall detection can be enabled and disabled by the user. 

watchOS 5

To go with the launch of a new smartwatch model, Apple introduced watchOS 5 on September 17, 2019

Along with fall detection for some older Apple Watch models and Series 4 support and updated watch faces to take advantage of the larger displays, watchOS 5's most accessible new feature was Walkie Talkie. After connecting Apple Watches via the app, users can open a line of communication in a similar way to the radio-based devices of the same name, with messages automatically playing aloud on the recipients' version. 

To encourage activity, a feature allows users to set up competitions with others, with progress in a number of areas monitored over time to determine the winner in a week-long contest. Throughout the week, participants can see the other's progress, giving them more opportunity to catch up if they are behind. 

Automatic workout detection can alert a user to a detected workout if one is sensed to be ensuing but not manually triggered. The feature can provide credit for existing exercise performed if an activity is confirmed, rather than starting from scratch at that moment. 

Apple Podcasts were added to watchOS in the release, with users able to request podcast playback via Siri. Third-party apps were also enabled to play background audio for the first time. 

Siri also gained the ability to trigger if the user raises their wrist to their face. This saves having to use the "Hey Siri" verbal prompt, which may be useful in situations such as those where the person needs to be relatively quiet. 


The customary disassembly of the Apple Watch Series 4 by iFixit showed Apple made many changes to the device's internal structure, including new buttons and a thinner display. Other components were optimized for space, such as the Taptic engine being smaller but longer. 

The barometric sensor was relocated inside the speaker grille, resulting in no longer having a separate hole as shown on the Series 3. 

Despite the case being approximately 6 percent thinner than before, the battery is slightly higher-capacity, growing from 1.07 watt-hours in the Series 3 to 1.113 watt-hours. 

The Apple Watch Series 4 has a small red ring on the Digital Crown to signify cellular devices The Apple Watch Series 4 has a small red ring on the Digital Crown to signify cellular devices

While battery replacements were deemed to be "pretty straightforward," the Apple Watch Series 4 was given a "repairability" score of 6 out of 10 due to screen replacements being "difficult but doable," the use of tiny tri-point screws, and the direct mounting of flex cables to the S4 system-on-chip. Most board repairs were deemed "impossible." 

Apple Watch Series 4 Pricing

Preorders for the Apple Watch Series 4 commenced on September 14, 2018, with shipments from September 21. The GPS and Wi-Fi model started from $399, while the Cellular variants started from $499. The Nike+ models started from $399, and the Apple Watch Hermes started from $1,249. It is no longer for sale by Apple.