Apple's iOS 26 update has the second-lowest adoption rate of all iOS releases since 2015, trailing only iOS 17. 79% of iPhones now run iOS 26, but this is below the 82% adoption rate of iOS 18 just a year ago. While iOS 26 is pre-installed on 86% of devices launched in the last four years, older versions like iOS 18 (14% of devices) and iOS 17 (7%) still linger. Critics point to the controversial Liquid Glass design language as a potential deterrent, though Apple claims iOS 27 will prioritize performance, with app speeds 30% faster on older hardware. iOS 27’s backward compatibility with iPhone 11 and newer models may boost future adoption.