When it comes to mobile data, where customers almost always have a limited pool of access to work with, less is more. That's the principle behind the "delta" updates to apps that Google introduced way back in 2012, which in most cases allows the Play Store to download only the incrementally updated parts of an app rather than the entire APK. Now a new tweak to the delta update algorithm has made the updates themselves even smaller.
How much smaller? According to the post on the official Android Developers Blog, two patches to older versions of Chrome for Android resulted in shrinking a major 22.8MB update down to 12.9MB, and a smaller one from 15.3MB down to just 3.6MB. Your mileage may vary, of course - a few "minor text fixes" (cringe) are going to result in a smaller update than, say, whatever it takes to fix that three footprint bug in Pokémon GO. But in general, developers and end users should be seeing dramatically smaller delta update sizes, and that's good news for anyone on a limited data plan.
The new delta algorithm can also be applied to expansion files, add-ons to the main app that are relatively huge, usually used for the resource files in large and complex mobile games. Google claims that applying this tool to initial downloads shrinks them by 12%, and updates are chopped by an impressive 65%. Not bad, not bad at all.
- Android Developers Blog