Is scroll to top with Android native back button a common pattern?

Question

I have noticed that e.g. Facebook and Instagram use the Android back button so that instead of taking you to the previous screen or out of the app, it takes you first to the top of page (if you have scrolled down). If you then click back again, then it takes you to the next screen or out of the app (as one would expect).

I tried to look in Material Design if this is an Android pattern, because it is quite handy instead of adding "scroll to top" buttons to pages and taking up valuable screen space. It seems that this is not however Android practice, but some companies have implemented this by themselves.

I think the problem with this is similar to gestures, it is not intuitive like "scroll to top" button. And if it breaks the back pattern used everywhere else, it can be confusing to users.

Now I'm wondering if our app should implement this feature. Is it well known or just used in a couple of apps? Have you run into examples of this behaviour? I tried Google-fu, but got nothing.

Answer 1

Here's an interesting article on back buttons that break the rules: https://baymard.com/blog/back-button-expectations

If the user perceives that they're "going back" to a previous page (and maybe that's the top of the page, if there's no pagination), then research suggests that the use of the back button is OK.

Answer 2

Use the back button to take the user to the top of the page when all the below conditions are satisfied

1. You have not more than 3 independent pages (screens) in your entire app.
2. The page is viewed more than 75% of the time.
3. The page length exceeds 1.5 x Total device length.

Additionally, you may use the back button to take the user to the top of the page in either of these cases:

1. The page is updated in a way that the latest entries are added to the top of the page.
2. The top menu bar scrolls along with the page.

Why use the back button to scroll to the top of the page?

1. Android users prefer pressing the home/menu button instead of the back button to close an application because many apps have a deep navigation tree. This will take multiple taps on the back button to close the app.

2. Scrolling up to the top of a long page is time-consuming.

3. Providing a scroll-to-the-top button occupies space which can make the app feel bloated.