Preact’s size and speed generally make it best suited for lightweight mobile web apps or web widgets and embeds where React might be too heavy for. Because of its minimalist nature, Preact is generally considered for smaller projects where performance is the primary concern.
To keep Preact as small and easy as it is, it focusses on the core values of React and misses things like PropTypes support or React’s synthetic events.
However, Preact provides a dedicated compatibility layer that can be used to leverage the many libraries of the React ecosystem and use them with Preact.
Preact can be used directly in the browser without any transpilation step in-between.