STREAMING CONTENT WON’T FULLY FILL SCREEN
Overview - 18:9 aspect ratio screen
When the LG G6 was first introduced to the marketplace, its 18:9 aspect ratio screen was new to the industry. It may still take some time for applications to provide native support for this resolution.
In the meantime, you may experience deception on account of how the content is rendered on screen based on the application you are using.
Many video players provide a function expanding the content to full screen. However, this is incumbent on the ratio of the content being played as well as whether the player supports this feature. For players that do not support it, you will notice vertical black bars on either end of the screen when the content is being played back. That is normal.
See a few examples below of content supporting different aspect ratios:
Whereas some Applications did not feature "Fill" or "Zoom" option for their 16:9 video content, such as YouTube, YouTube now supports Full screen on an 18:9 device. Original 16:9 video content now offers zooming option to fill the screen. Be cognizant that in order to maintain accurate proportions on screen the picture will require to be cropped thus eliminating some picture details at the very top and bottom.
Just ensure the YouTube application software on your phone has been updated to version number 12.41.55 or greater.