Performance
Critical CSS
Plain-language definitionThe minimum styles needed to render the first visible portion of a page. Delivering them early can prevent a blank or unstyled first view.
Why it matters
Use the term to make a better decision.
In practice, critical css matters when a team needs to connect a technical or creative choice to a visible change in clarity, performance, discovery, or conversion. The useful question is not whether the term sounds sophisticated. It is what decision it helps the team make.