Improved mobile hardware, increased storage, and faster data networks allow developers to make advanced, beautiful, expansive games for pocket-sized devices. But small screens don't mean small downloads, and some of today's mobile games get BIG. While that's not usually a problem for Wi-Fi connected players, it can cost you dearly when it comes to players who want to download your game over cellular data.
Over the last few years, we've seen the over-the-air (OTA) limit for the App Store climb from 25MB up to its current size of 100MB (Google Play mandates an initial APK under 50MB) as both device capabilities and game sizes have increased. Nonetheless, many mobile games are much larger than 100MB. App Store Editor's Choice Transistor, for example, is a whopping 1.84GB. So what do you do when your amazing game is too chunky to fit through a cellular antenna?
Well, you could do nothing and just mandate a Wi-Fi connection to download. I mean, they're pretty ubiquitous these days, right? True, but for a handset-compatible app, exceeding the OTA limit can reduce your downloads by up to 50%, and impact first session after install numbers just as much. Mobile players are fickle, and you have about three minutes from the time you catch their attention in-store to get them engaged with your game. Exceeding OTA means they have to come back to your game at some later time. Guess what, they won't.
(The exception: Premium games can often get away with large files, particularly if they are relatively expensive, and/or do not rely on secondary monetization. The same is also true of highly-recognized brands where players are willing to overcome a higher barrier to entry in order to engage with your game. You say you're not working on the next Grand Theft Auto? Keep reading.)
Your first instinct might be to trim your game down to fit the limits. If you're very close to the 100MB (or 50MB for Android) limit, that might work initially. But what about after you've released three content expansions? Or what if your game is simply nowhere close, like Transistor? In these cases it's just not feasible to shoehorn an entire big game into a small package.
But what about just part of the game?
Brand new players don't need every asset of your elder game, DLC, or late stage features. They need titles, navigation, and your first-time user experience - that's it.
So instead of forcing players to download your entire game at once, build a small initial download that covers just what is needed for the first 15-20 minutes of gameplay. Then do a background download on iOS (you would use APK expansion files on Android) for everything else once the initial app is installed.
This provides the best of both worlds: an OTA-compliant download to improve installs and engagement and then eventually all the robust features, functionality, and graphics of a larger app.