Google flips the switch on "Smart Updates" in the Google Play, that eliminates the need of downloading a full Android app when there is an update available on the Store--which at times is quite painful (specially on larger apps) and also consumes bandwith and battery.
With "Smart Updates," which was first announced during the Google I/O back in June this year, only the parts of the app that have changed would be downloaded.
"When enabled, only the incremental difference (a.k.a. the delta) between the old and new apks would be sent over the wire, thereby saving huge amounts of data for both Google and Play Store users."
These incremental "smart" updates went live recently, with the release of the version 3.8.15 of Google Play Store. As the change seems to be retroactive and server-side, it should also work with earlier Play Store releases.
Android Police, who first reported the news, posted a screenshot and a video showing the update to ezPDF Reader app, which usually weigh in at about 6.3MB, but now clocks in at under 3MB.
And, the Instagram's update from this morning went down to 3MB out of 13MB.
Note: This feature "only" works, when you connect your to Google Play on you smartphone with mobile phone internet connection. Those who, share their desktop broadband on phones through Wi-Fi and those who download ".apk" on their desktop, would still have to download complete app.
Watch the two videos embeded below showcasing smart app updates: