Android: ScrollView vs NestedScrollView

NestedScrollView as the name suggests is used when there is a need for a scrolling view inside another scrolling view. Normally this would be difficult to accomplish since the system would be unable to decide which view to scroll.

This is where NestedScrollView comes in.

In addition to the nested scrolling NestedScrollView added one major functionality, which could even make it interesting outside of nested contexts: It has build in support for OnScrollChangeListener. Adding a OnScrollChangeListener to the original ScrollView below API 23 required subclassing ScrollView or messing around with the ViewTreeObserver of the ScrollView which often means even more work than subclassing. With NestedScrollView it can be done using the build-in setter.

Other than the advantages listed in the answers given, one more advantage of NestedScrollView over ScrollView is its compatibility with CoordinatorLayout. The ScrollView does not cooperate with the CoordinatorLayout. You have to use NestedScrollView to get "scroll off-screen" behaviour for the toolbar.

Toolbar will not collapse with Scrollview as child of CoordinatorLayout

NestedScrollView

NestedScrollView is just like ScrollView, but it supports acting as both a nested scrolling parent and child on both new and old versions of Android. Nested scrolling is enabled by default.

https://developer.android.com/reference/android/support/v4/widget/NestedScrollView.html

ScrollView

Layout container for a view hierarchy that can be scrolled by the user, allowing it to be larger than the physical display. A ScrollView is a FrameLayout, meaning you should place one child in it containing the entire contents to scroll; this child may itself be a layout manager with a complex hierarchy of objects

https://developer.android.com/reference/android/widget/ScrollView.html