Dev server and instant HMR over native ESM

Vite was created to fix painfully slow dev server startups, sluggish hot updates, and long build times by rethinking how code is served during development. Instead of bundling the entire application upfront, it splits the work in two: dependencies that rarely change are pre-bundled once using fast native tooling so they are ready instantly, while application source code is served on-demand over native ES modules — the browser loads only what the current page needs and Vite transforms each file as it is requested. Dev server startup is therefore nearly instant regardless of application size, and editing a file triggers Hot Module Replacement (HMR) over native ESM that updates just that module in the browser, with no full page reload or rebuild wait. Unbundled ESM still ships poorly in production because nested imports add network round trips, so optimized production builds remain bundled. Vite's plugin API follows Rollup's conventions, and the toolchain is now unified on Rolldown, a Rust bundler that uses Oxc for parsing, transforming, and minifying. Scope: Vite. Reviewed October 4, 2026.