React

React remains the most widely used frontend library for good reason: its component model maps naturally to how we think about interfaces, and its ecosystem is unmatched in depth and breadth. When you choose React, you gain access to thousands of battle-tested libraries, extensive hiring pools, and answers to virtually every question you could encounter.

The introduction of Server Components with React 19 fundamentally changed the data-fetching story. Components can now run on the server, fetch data directly, and send rendered HTML to the client - reducing bundle size and improving performance without the complexity of separate API layers.

For startups, React's flexibility is both its strength and its challenge. It does not prescribe architecture, which means you need to make good decisions about state management, routing, and data fetching. This is why most teams pair React with a meta-framework like Next.js that provides these opinions.