innerHeight property returns the height of the content area of a window
vh = 1% of the height of the viewport size

5 Units can be used with CSS to fix mobile issues; if you use a unit that does not match the innerheight, the user visiting your site may not see some absolute or fixed buttons because they are hidden by the navigation bar.
One of the browsers most affected by this problem is Webkit-based, so several units have been introduced over the years to compensate for the problem.
These tests can be used to check the value of each unit.

100vh position:fixed
100lvh position:fixed
100svh position:fixed
100dvh position:fixed
100% position:fixed
100vh position:absolute
100lvh position:absolute
100svh position:absolute
100dvh position:absolute
100% position:absolute
CSS fix for 100vh 100vh in Safari CSS 100vh Mobile Browsers It’s not a bug, it’s a feature The trick of Viewport Units Avoid 100vh on Mobile Web WebKit Bugzilla Matt Smith Solution