In 2011, we saw the first HD displays with a 16:9 aspect ratio. Since then, 16:9 had grown to become the standard for display aspect ratios on Android. However, things changed this year, as multiple smartphone manufacturers launched displays with taller display aspect ratios. Xiaomi started it all with the 17:9 aspect ratio display of the 2016 Mi Mix, but it was Samsung and LG who popularized 18:9 and even taller aspect ratio displays on Android with the Galaxy S8/S8+ and the LG G6 respectively.
The taller 18:9 (2:1) display aspect ratio has been widely acclaimed by users as it allows the width of the device to remain comfortable enough for one handed use. This is because 18:9 displays are narrower than equivalently-sized 16:9 displays.
However, the change has been affected with its own share of issues. In the beginning, many apps did not play well with the taller aspect ratio, but since then, Google has released new guidelines for developers to specifically target the 18:9 aspect ratios. The app situation, therefore, has been slowly improving. A bigger problem, though, was media content such as YouTube videos, which are shot for the widescreen 16:9 aspect ratio. Viewing 16:9 media content on an 18:9 aspect ratio display led to black bars being visible on both sides, which means that the screen size was effectively reduced.
Samsung implemented a crop zoom option to enable users to watch YouTube and other videos on the Galaxy S8/S8+/Note 8 without having to see black bars on the display. However, other manufacturers like LG did not include such an option, and users were stuck watching videos with black bars instead of cropping the video by pinch-zooming. Clearly, this was a sub-optimal situation.
Therefore, Google recently released an update to YouTube, bringing the version number up to v12.40 and adding pinch-to-zoom on videos for the 18:9 Pixel 2 XL. The Pixel 2 XL is only a single device, though, and the update left users of other 18:9 devices such as the Galaxy S8, LG G6, LG V30, Xiaomi Mi Mix 2, etc, out of luck.
Now, YouTube has been updated to v12.44, and it brings pinch-to-zoom for more devices with 18:9 displays. AndroidPolice was able to confirm that the functionality now works on the Galaxy S8+. It is also expected to work on other 18:9 devices such as the LG V30, Xiaomi Mi Mix 2, OnePlus 5T, etc. The functionality will improve the experience of watching YouTube videos on 18:9 smartphones and since it does not take away from existing solutions, there is no downside to having an additional option for users to choose from.