Google added support for delta app updates ages ago to save you from re-downloading an entire app every time there's an update. That's all well and good, but the process hasn't been very transparent. Now, it looks like the Play Store has started showing the size of an update rather than the full app size.
If you check an app description in the Play Store prior to downloading an app, it shows the full download size. This makes sense, of course. After you install it, not so much. Once installed, the Play Store doesn't actually show the download size at all until there's an update. The size shown then corresponds to the size of the patch—how much data you actually need to download to update the app. In the screenshots, you can see Chrome Beta reporting a size of 15MB. That's definitely not the full app, but it matches the update size perfectly.
The progress bar now matches the displayed update size, which makes it less confusing. Previously, it displayed the full app size and would just stop after the patch was downloaded. We're seeing this on a few devices, so it appears to be a wide rollout. Google may have quietly made this change recently on its end as it is pretty subtle. Just take a peek at the app info to see your own update sizes.
- Kapil Faujdar