Vivo ships the S1 with FunTouch OS running on top of Android 9 Pie. It has customisations and comes with a few apps preinstalled. The Vivo S1 is powered by a MediaTek Helio P65 SoC and is the first smartphone in India to do so. There are three variants of the Vivo S1, 4GB RAM with 128GB storage, 6GB RAM with 64GB of storage and 6GB RAM with 128GB of storage. We had the top-end variant for review and it did not face any issues in day-to-day usage.We played games like PUBG Mobile which the S1 ran at medium settings. The phone did get warm to the touch after gaming for 20 minutes. The camera is where the S1 still needs some work as we weren't happy with its performance. It does a decent job in daylight but delivers below-average performance in low-light. The 4,500mAh battery offers good battery life and Vivo does ship an 18W fast charger in the box.