Babel

Babel is a JavaScript compiler that enables developers to use next-generation JavaScript syntax today by transforming it into backwards-compatible versions that older browsers can execute. It parses modern JavaScript including features like optional chaining, nullish coalescing, and class fields, then outputs equivalent code using only syntax that target environments support.

Babel operates through a plugin architecture where each syntactic transformation is a separate plugin. Presets bundle related plugins together for convenience. The most common preset, @babel/preset-env, automatically determines which transformations are needed based on a specified browser support target, avoiding unnecessary transformations that would bloat the output. Babel also handles JSX transformation for React and TypeScript stripping.

For web development, Babel has been a foundational tool in the JavaScript ecosystem since 2014, enabling the industry to adopt ES2015+ features years before browsers fully supported them. While its role has narrowed as browser support improved and faster alternatives like esbuild and SWC emerged, Babel remains relevant for projects requiring fine-grained control over syntax transformations or custom plugins.