Vast majority of all iPads, iPhones in service use iOS 13
Apple has updated its iOS 13 adoption numbers, with more than three-quarters of all iPhones introduced in the last four years on the new operating system.

Dark mode on iOS 13
In a post made on Apple's developer's website, Apple has detailed the adoption of its modern operating systems. Beyond 77% of users with devices four years old or less on iOS 13, 70% of all devices in service use iOS 13.
Apple's iOS 12 still has a strong -- but shrinking -- showing. Use of iOS 12 has shrunk to 23% of all iPhones, versus 38% in October.
Operating system upgrade rates for the iPad are a slightly different matter. Presently, Apple's data says that 79% of all the devices released in the last four years are on iPadOS, with 19% on iOS 12. For all iPads, 57% are on iPadOS, with 27% on iOS 12, and 16% on earlier operating systems.
Adoption rates remain similar to that of iOS 12 over iOS 11. In early January 2019, iOS 12 was on 78 percent of all iPhones, iPads, and iPod touches shipped in the prior four years. Broadening analytics to all Apple mobile devices, iOS 12 usage was 75 percent.
Introduced alongside iPhone 11 and 11 Pro in September, iOS 13 offers users an array of new features including Dark Mode, the "Sign in with Apple" single sign-in tool, revamped first-party apps, new camera features and much more.
Apple has since issued multiple point updates to patch bugs and security holes discovered after launch. The operating systems are now up to iOS and iPadOS 13.3.1, which was released earlier on Tuesday.

Dark mode on iOS 13
In a post made on Apple's developer's website, Apple has detailed the adoption of its modern operating systems. Beyond 77% of users with devices four years old or less on iOS 13, 70% of all devices in service use iOS 13.
Apple's iOS 12 still has a strong -- but shrinking -- showing. Use of iOS 12 has shrunk to 23% of all iPhones, versus 38% in October.
Operating system upgrade rates for the iPad are a slightly different matter. Presently, Apple's data says that 79% of all the devices released in the last four years are on iPadOS, with 19% on iOS 12. For all iPads, 57% are on iPadOS, with 27% on iOS 12, and 16% on earlier operating systems.
Adoption rates remain similar to that of iOS 12 over iOS 11. In early January 2019, iOS 12 was on 78 percent of all iPhones, iPads, and iPod touches shipped in the prior four years. Broadening analytics to all Apple mobile devices, iOS 12 usage was 75 percent.
Introduced alongside iPhone 11 and 11 Pro in September, iOS 13 offers users an array of new features including Dark Mode, the "Sign in with Apple" single sign-in tool, revamped first-party apps, new camera features and much more.
Apple has since issued multiple point updates to patch bugs and security holes discovered after launch. The operating systems are now up to iOS and iPadOS 13.3.1, which was released earlier on Tuesday.
Comments
iPads that are PC replacements are going to get updated a lot more than ones for a specific task. If an iPad is only used a few times a week, there’s not going to be a lot of motivation (awareness of security risk) to upgrade.
Apple does EVERYTHING POSSIBLE to force you to upgrade-- when I wanted to pair an Apple watch to my iPhone 8 running iOS 12 it FLAT OUT REFUSED to allow it to pair without upgrading the phone to iOS 13 and watchOS 6. This watch was running watchOS 5 and had been previously paired to an iPhone 5s running iOS 12.4, and the iPhone 8 was running 12.4 as well.
I *really* didn't want to go to 13 at that time but I was given the choice of leaving the watch in a drawer or upgrading.
I finally updated my devices to iOS 13. It at least seems semi-safe at this point. What in the $*(# were they thinking with the new volume system, though? And, the App Store and updates? And Photos new UI? And, Notes URL touch-targets being like 2x the size of the link text (so you almost can't edit the text around them). Oh my.
I'm hoping the updates to Safari will make it worth it, though, and I suppose one has to try to stay current these days.
I'm curious about the Mojave and iOS 13 Notes sync issue you mentioned though. I've been using them together and everything seems OK so far. Should I be scared?