How does Vite work, and why is it so fast in development compared to webpack?

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Accepted Answer

Vite, created by Evan You, the creator of Vue.js, revolutionizes the frontend development experience through a fundamentally different approach to bundling.

The traditional webpack approach.

webpack analyzes all your code, resolves all dependencies, and creates a complete bundle before starting the development server. The larger your application grows, the slower this cold start becomes. For a large application, this can take several seconds or even minutes.

The Vite approach in development.

First, no initial bundling. Vite starts the server immediately without bundling the application. Cold start is nearly instant, typically one to two seconds.

Second, native ES modules. Vite serves files directly to the browser using native ES modules. The browser handles imports itself. When you import a module, the browser makes an HTTP request for that file.

Third, on-demand transformation. Vite only transforms a file when the browser requests it. If you do not visit a page, its code is never processed.

Fourth, esbuild for dependency pre-bundling. Dependencies from node_modules are pre-bundled with esbuild, which is ten to one hundred times faster than JavaScript bundlers. This happens once and is cached.

Fifth, ultra-fast HMR. Hot Module Replacement only updates the modified module, not the entire application. Since there is no bundle to rebuild, HMR typically takes ten to twenty milliseconds.

In production.

Vite uses Rollup for the production build. Rollup produces optimized bundles with excellent tree shaking. The behavior in production is therefore different from development.

When Vite is the right choice.

For new projects, Vite is generally the best choice. For existing webpack projects, migration is worthwhile if development slowness impacts productivity.