Youtube will soon change its UI where the main navigation bar will be moved from the top to the bottom of the app. This is part of the latest update to the YouTube app. YouTube has been testing a new UI for its Android app for some time now. This has gone through a few different iterations throughout the testing phase.
Google stated that this new update for Android will make the YouTube experience more consistent across its mobile platforms. The navigation bar on the bottom now shows the Home, Trending, Subscriptions, and Library options. Library section has now been separated from the previous Account option, which can now be accessed on the top bar of the app in the profile icon, along with Settings. Any videos you have uploaded or purchased are in the Library section, while also including your YouTube watch history and playlists.
The bottom navigation bar should be available on all YouTube app pages, with the exception of when you actually watch videos. Google adds that the YouTube Android app will also remember where you left off on each tab, which should make it easier to navigate