Last year, Android users installed 65 billion apps - that's a lot of Internet traffic. To address that, Google has updated its delta and compression algorithm making both initial installs and especially updates much smaller.
Android apps are limited to a 100MB APKs, but can use the APK Expansion Files feature to bring in an additional 2GB (mostly used for game assets). The new algorithms can save up to 12% on first install and as much as 65% when updating. That's a lot when we're talking 2GB of data!
Then there are the APKs themselves. Google specifically tuned the new algorithm, called bsdiff, to handle native code libraries and it outperforms the old algorithm by as much as 50%.
Here's how bsdiff reduces Chrome update downloads. The major update is cut almost in half, while the minor update is four times smaller than what the old algorithm managed.
Chrome patch Description Previous patch size Bsdiff Size
M46 to M47 major update 22.8 MB 12.9 MB
M47 minor update 15.3 MB 3.6 MB
Note that for apps that don't contain native libraries, there's still a small gain of about 5%.
Google is going to showcase transfer sizes - both in the case of first install and of updating an existing app. That's great news for users that do their updates on a limited Internet plan.
Play Store gives more info on size: App size for initial install • App size when updating
The Chrome teams also has a few tips for app developers on how to reduce download sizes, check the Source link for more.