Apple S4

<style>
.ios-ib th.ios-lab { background-color: #333; color: #fff; text-align: center; width: 28%; padding: 6px; }
.ios-ib td.ios-val { text-align: left; padding: 6px 10px; }
</style>
{| class="ios-ib" style="width: 100%; border: 2px solid #333; text-align: center;" darkstyle="border-color: #48484a;"
|-
| colspan="2" style="padding: 28px 20px 42px;" |
<div style="font: bold 2em/1.2 -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Helvetica Neue', Helvetica, Arial, sans-serif; color: var(--wiki-color);">Apple S4</div>
|-
! class="ios-lab" | Designer
| class="ios-val" | [[Apple]]
|-
! class="ios-lab" | Introduced
| class="ios-val" | September 2018 (Apple Watch Series 4)
|-
! class="ios-lab" | Type
| class="ios-val" | System in Package (SiP)
|-
! class="ios-lab" | CPU
| class="ios-val" | Dual-core, 64-bit (first in Apple Watch) — ~2× faster than [[Apple S3|S3]]
|-
! class="ios-lab" | Wireless
| class="ios-val" | [[Apple W3|W3]] wireless chip
|-
! class="ios-lab" | Devices
| class="ios-val" | Apple Watch Series 4
|-
! class="ios-lab" | Predecessor
| class="ios-val" | [[Apple S3]]
|-
! class="ios-lab" | Successor
| class="ios-val" | [[Apple S5]]
|}

{{Apple silicon Navbox}}

The Apple S4 brought the Watch into the 64-bit era in September 2018, doubling performance with custom Apple cores. Its bigger story was sensing: a next-generation accelerometer and gyroscope enabled fall detection, and electrodes in the crown and back supported the Series 4's ECG app — the feature that turned the Apple Watch into a regulated health device.

= Legacy =

The S4 generation is where the Watch's health pivot happened in silicon — ECG, fall detection, and the 64-bit foundation that watchOS still requires. Its core design carried nearly unchanged through the [[Apple S5|S5]], setting up the S series' pattern of sensor-led rather than speed-led years.