The View Transitions API is a new — but game-changing — feature that allows us to do the types of reactive state-based UI and page transitions that have traditionally been exclusive to JavaScript frameworks. In the first part of this mini two-part series, Adrian Bece thoroughly explains why we need the API and demonstrates its basic usage.

Since the introduction of CSS viewport units in 2012, many of us have been using width: 100vw as a way to set an element’s width to the full width of the viewport. But, as Šime Vidas explains in this deep dive, 100vw does not always represent the full width of the viewport due to differences in how browsers handle scrollbars.