Develop, build, and preview

The three main commands answer different questions.

npm run dev

The development server favors fast feedback. A route is rendered when you open it locally.

npm run build

The production build checks imports and creates deployable output. In a static project, every known route is rendered to files under dist/ by default.

npm run preview

Preview serves the built output locally. It lets you inspect the generated routes and assets without rebuilding on every request.

Development success is not build success. A dynamic route may be missing a path. A content entry may fail its schema. A source filename may differ only by case.

Preview is also not the real host. Redirect status codes, headers, and server routes can depend on the platform.

Run all three commands. Write down when the page code ran in each mode.