Dynamic Viewport Units

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To size something as tall as the viewport, you can use the vw and vh units.
There, the viewport size is influenced by the presence or absence of dynamic toolbars. These are user interfaces such as address bars and tab bars
To solve this problem, the various states of the viewport have been specified at the CSS Working Group.
Large viewport: The viewport sized assuming any UA interfaces that are dynamically expanded and retracted to be retracted.
Small Viewport: The viewport sized assuming any UA interfaces that are dynamically expanded and retracted to be expanded
Units representing the large viewport have the lv prefix. The units are lvw, lvh, lvi, lvb, lvmin, and lvmax.
Units representing the small viewport have the sv prefix. The units are svw, svh, svi, svb, , and