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Next.js automatically optimizes your app to be static HTML whenever possible. Learn how it works here.

Automatic Static Optimization

Next.js automatically determines that a page is static (can be prerendered) if it has no blocking data requirements. This determination is made by the absence of getInitialProps in the page.

This feature allows Next.js to emit hybrid applications that contain both server-rendered and statically generated pages.

Statically generated pages are still reactive: Next.js will hydrate your application client-side to give it full interactivity.

One of the main benefits of this feature is that optimized pages require no server-side computation, and can be instantly streamed to the end-user from multiple CDN locations. The result is an ultra fast loading experience for your users.

How it works

If getInitialProps is present, Next.js will use its default behavior and render the page on-demand, per-request (meaning Server-Side Rendering).

If getInitialProps is absent, Next.js will statically optimize your page automatically by prerendering the page to static HTML. During prerendering, the router's query object will be empty since we do not have query information to provide during this phase. Any query values will be populated client-side after hydration.

next build will emit .html files for statically optimized pages. For example, the result for the page pages/about.js would be:

.next/server/static/${BUILD_ID}/about.html

And if you add getInitialProps to the page, it will then be JavaScript, like so:

.next/server/static/${BUILD_ID}/about.js

In development you'll know if pages/about.js is optimized or not thanks to the included static optimization indicator.

Caveats

  • If you have a custom App with getInitialProps then this optimization will be disabled for all pages.
  • If you have a custom Document with getInitialProps be sure you check if ctx.req is defined before assuming the page is server-side rendered. ctx.req will be undefined for pages that are prerendered.