Apple has mostly kept iOS and macOS separate from each other, but there are instances where Apple lets users sync certain features across iOS and macOS, such as Messages, Notes, Calendars, and so on. There have been rumors that Apple would merge both platforms, but Apple has denied such claims.
However instead Apple could be taking a page out of Google’s book and create a feature that would allow apps to run cross-platform. This is according to John Gruber at Daring Fireball (via 9to5Mac) who has heard from second-hand sources about the rumored feature. It is unclear as to what exactly this could mean, but from what it sounds like, developers could create universal apps that can run on either iOS or macOS devices without having to develop two separate versions of it.
This is actually not the first time that there have been rumors about universal apps in Apple’s ecosystem. Back in December 2017, Bloomberg’s Mark Gurman published a similar-ish report, except that Gurman claimed that Apple would be launching the feature in 2018 with iOS 12 and macOS 10.14, but Gruber is suggesting that it will only be coming in 2019 at the earliest.
It is possible that Gurman’s initial report could have been right, but given that there is a more recent report about how Apple is delaying iOS 12’s major features to 2019, perhaps this universal app feature could have been one of those major features delayed. Either way take it with a grain of salt for now, but we suppose we’ll have to wait until 2019 to find out if it is true or not.