Back when Google announced Android 4.1 Jelly Bean, it also shared a couple changes coming to the Google Play Store. While we liked what we heard, it hasn’t been smooth sailing for all those new features; the new app encryption that was supposed to discourage piracy has ended up causing quite a few headaches for developers struck by an app-disabling bug. That’s why we’re relieved to see that another change seems to be going a whole lot more smoothly, now that word’s surfaced that Google has enabled delta updates.
Delta updates are the same sort of thing Apple introduced with its firmware updates in iOS 5; in mathematics, the Greek delta symbol indicates the change between two values. Here, instead of downloading a whole app over again whenever a new version comes out, Google’s servers will just deliver the portion that’s changed, or is new. That can mean the difference between a 20MB and a 2MB download. When you’ve got a fast connection, pulling down the full app each time is no problem, but when your signal’s a little weaker, or you’re pushing the limits of your data plan’s allowances, having to download a whole lot less data each time you upgrade can be a godsend.
It looks like you don’t even need the latest Play Store update for this feature to work; you should start noticing the change with updates that have been published to the Store over the last couple days.
Source: Android Police