Apple’s iOS 10 mobile operating system is now installed on more than two thirds of active iPhones, iPads and iPod touches. This is the fastest adoption rate of any of the past updates as many believed that it would lag behind iOS 9.

It was recorded that 66.7 percent of Apple’s devices are running iOS 10 twenty-seven days after it was released, according to Fiksu. On a separate recording, Mixpanel says that adoption rate has reached 66 percent. Both Fiksu and Mixpanel track iPhones and iPads that are using the web, according to 9To5Mac.

Fiksu Graph Of iOS 10 Adoption Graph showing iOS 10 surpassing its predecessors. Photo: Fiksu DSP

Before the release of iOS 10, iOS 9 was installed on 88 percent of devices. Now, there are more iPhones, iPads and iPod touches running iOS 10 than iOS 9. The spike in adoption is said to be unprecedented as it was initially believed that iOS 10 would lag behind iOS 9 for months. iOS 10 was actually behind iOS 6, iOS 7, and iOS 9 and only surpassed its predecessors two weeks after its release, according to Digital Trends.

Adoption to iOS 10 spiked around Sept. 27 with a recorded increase of 20 percent until Oct. 4. It is believed that users who bought the iPhone 7 and iPhone 7 Plus contributed to the fast adoption rate of the software, but it doesn’t necessarily explain the sudden spike.

Mixpanel's Graph iOS 10 Adoption Mixpanel's graph clearly showing a spike in iOS 10 adoption. Photo: Mixpanel

It’s important to note that Apple doesn’t force its users to update to the latest software, and most of the first adopters simply checked for the updates themselves. However, Apple does send out notifications for the updates a couple of weeks after the release of iOS 10. It’s possible that the spike might have been triggered by the release of iOS 10.0.2 on Sept. 23 which should have notified users.

When Apple first released iOS 10, many users complained that the update seemingly bricked their devices. Other users may have held off from updating due to that issue and may have simply waited for a more stable version of the software. Whatever the case may be, iOS 10 is now the most popular version of Apple’s mobile operating system.