Apple has provided iOS 18 adoption statistics on its official developer page.
In the report, iOS 18 is on the same adoption rate page as iOS 17, with the software being installed on 76% of iPhone models that were introduced in the last 4 years. On the iPad side, iPadOS 18 has been installed on 63% of iPad models that were introduced in the last 4 years. In its entirety, iPadOS 18 is in 53% of all iPad models while iOS 18 is in 68% of all iPhone models. It’s worth noting that this is the first time Apple made this data available since the software was released.
In comparison, iOS 17 was on 76% of iPhone models in the last 4 years, while iPadOS 17 was on 61% of iPad models in the last 4 years. Major features on iOS 18 include Apple Intelligence, currently limited to the iPhone 16 and iPhone 15 Pro lineup.