esbuild is a bundler, a build tool that follows the import statements of a web project and combines its many source files into a few output files that a browser or Node.js can load. It was created by Evan Wallace and is developed in the open on GitHub.
esbuild is written in Go and compiles to native code, and it spreads parsing and code generation over all CPU cores. Its home page shows a production bundle of ten copies of the three.js library taking 0.39 seconds, against 14.91 seconds for Parcel 2 and 41.21 seconds for webpack 5. It handles JavaScript, CSS, TypeScript and JSX without plugins, bundles both ESM and CommonJS modules, and does tree shaking (removal of unused code), minification and source maps. It can be driven from the command line, a JavaScript API or a Go API, and it offers a watch mode, a local server and a plugin API.
esbuild is free and open source under the MIT License.