iPad Apps Are Coming to Your Mac: Here’s What to Expect from Project Catalyst

It’s been almost two years since we first heard about Project Marzipan, Apple’s initiative that would unify the worlds of iOS and macOS by basically allowing the same apps to run on both platforms.

Although the original plan raised concerns among long-time Mac developers and other Apple enthusiasts, the premise was always a sound one — provide the necessary tools that would allow developers to easily “port” apps built for the iPad over to the Mac without having to rewrite significant chunks of code. However, Apple’s attempt at demonstrating what this would be like — in the form of Home, News, Stocks, and Voice Memos in macOS Mojave — didn’t do much to mollify those who were already fearing the “dumbing down” of the Mac platform, and when news surfaced that Apple was going to give iTunes the same treatment, many feared the worst.

Fortunately, following the unveiling of macOS Catalina last month and the official release of the Marzipan framework, now known as Project Catalyst, it appears most of these fears were completely unfounded. The new macOS Music app is really just iTunes by another name, retaining all of the music features of its predecessor while losing the bloat of podcasts, movies, TV shows, and audiobooks, not to mention iOS device management. Similarly, it was more recently revealed that the original “Marzipan Four” were simply a bad design decision, not a reflection on the limitations of the actual Marzipan/Catalyst framework.

A Deeper Look at Project Catalyst

Nonetheless, as much as the official debut of Project Catalyst has assuaged most of the concerns that it would simply turn the Mac into a glorified iPad, there are still more than a few questions that remain. To attempt to get to the bottom of what all of this will mean, Ars Technica spoke with several senior Apple directors and engineers along with a handful of veteran iOS and Mac developers, including Todd Benjamin, Apple’s senior director of marketing for macOS, along with developers and software engineers at Gameloft, TripIt, and Twitter who are already using Catalyst to bring their iPad apps over to the Mac.

While the interview covers a lot of technical details that are primarily of interest to developers, it also answers a few burning questions about what we can expect from Apple’s new cross-platform initiative once it lands in the fall.

Why is Apple Doing This?

To be clear, Apple’s main goal for Project Catalyst is to reawaken a thriving ecosystem of Mac apps by letting it share in the success of the burgeoning iPhone and iPad App Store. While the Mac has had its own App Store since early 2011, it’s never seen the same level of popularity as its iOS counterpart, despite boasting a collection of powerful apps. Some of this may simply be due to the fact that macOS apps don’t have to come from the Mac App Store, but the platform hasn’t been without its other challenges either, creating new restrictions for developers that didn’t previously exist for apps downloaded from outside of the Mac App Store.

Either way, however, Apple is certainly hoping that giving iOS developers an easy way to transition their successful iPad apps over to the Mac will be a shot in the arm for the Mac App Store, and from what we’ve seen thus far, it already looks promising; even developers like Twitter, which previously abandoned their Mac apps, have already announced a return to the platform.

What This Means for Developers

Without getting into too much of the technical stuff, the main upshot for developers is that Catalyst will handle all of the difficult and tedious aspects of porting an app from a touchscreen-based iPad to a mouse-driven Mac, and will basically do this just by rebuilding their iPad apps for the Mac.

Of course, the reality is that there’s much more to it than that. A simple one-click rebuild is going to create an iPad-like Mac app that won’t be particularly appealing — we all saw how well that worked out with the original Marzipan Four, and in fact those apps will likely serve as examples for developers of what not to do. The important point, however, is that developers will be able to get past the resistance of dealing with all of the boring work of porting an app across platforms, focusing instead on the more creative and interesting design aspects of making a user interface that looks and works well on the Mac.

What This Means for End Users

For end users, the simplest explanation is that this means that there will be a whole range of new apps for the Mac platform. Further, this has been done in such a way that users don’t need to be concerned that developers are just going to port over simplified versions of iOS apps either — all of the tools are here to create rich Mac experiences.

It’s also important to note that it will not even be possible to bring iPhone apps directly over to the Mac — the source apps have to be iPad apps to be fed into Catalyst. While this may be surprising, as there are a great many more iPhone apps than iPad apps on the iOS App Store, Apple says it wants to make sure that what ends up on the Mac is appropriate for the platform.

Just design-wise, the difference between an iPad app and an iPhone app is that the iPad app has gone through a design iteration to take advantage of more screen space. And as you bring that app over to the Mac… you have something that’s designed around that space that you can work with and that you can start from.

Todd Benjamin, Senior Director of Marketing for macOS

That said, Catalyst isn’t going to be a panacea for all Mac development. Apple’s team has made it absolutely clear that the traditional development environment — known as “AppKit” — will still be fully supported, and will be a better option for developers building much more sophisticated Mac apps for power users and creative professionals. It’s also worth noting that developers can still mix AppKit code into Catalyst to get the best of both worlds.

There Will Be Games Too

Lest you think that this is just about bringing over apps like Twitter and productivity apps, Ars Technica also spoke to developers from Gameloft who have already successfully used Catalyst to bring Asphalt 9: Legends from the iPad over to the Mac, successfully, and — most importantly — easily.

In fact, Gameloft’s Alex Urbano said the process of porting the game was surprisingly easy, with Catalyst handling all of the issues that would understandably result with moving between vastly different CPU and GPU platforms. While no small amount of tweaking was required to get things just right, some of it was merely to improve the experience on the Mac by taking advantage of the more powerful hardware. Gameloft’s engineers said that it took about 24 hours to port the entire game over, which is actually pretty astonishing, and should be especially encouraging, since gaming is one of the areas in which the Mac platform has fallen significantly behind.

The Future of Catalyst on the Mac

The interview goes on to talk about where Apple is ultimately headed, and it’s definitely worth a read for those interested in all of the more technical details. To summarize, however, Apple’s long-term goal is to gradually shift all developers over to “SwiftUI” — a new common development platform that will allow developers to build new apps for both the iPad and Mac. While Catalyst is designed to take already existing iPad apps and move them to the Mac, Apple definitely prefers that developers simply start out by building a common app for both, rather than creating an iPad app first and then moving it to the Mac.

For now, however, all of these things are available in a developer’s tool belt, allowing them to choose the best options available for the task at hand, which is exactly the way Apple wants it. For the past several years, Apple has seemed to be putting a lot more emphasis on iOS than on the Mac, so it’s great to see these latest moves toward helping the entire ecosystem succeed. While the Mac will undoubtedly remain a distinct platform for the foreseeable future, common apps are going to be a huge boon to making Apple’s world feel a lot more unified.