What does `generateStaticParams` do, and how does `dynamicParams` affect it?

// app/blog/[slug]/page.tsx
export const dynamicParams = false;

export async function generateStaticParams() {
  const posts = await getPosts();
  return posts.map((post) => ({ slug: post.slug }));
}

export default async function Page({ params }: { params: Promise<{ slug: string }> }) {
  const { slug } = await params;
  return <Post slug={slug} />;
}

generateStaticParams returns the list of params to prerender at build time. dynamicParams decides what happens to params that are not in that list.

generateStaticParams runs at build time in a dynamic route, like app/blog/[slug]. Each entry it returns becomes a static page. It replaces getStaticPaths from the Pages Router.

dynamicParams controls params that were not returned:

true (the default): they render on demand the first time someone requests them.
false (export const dynamicParams = false): any other value returns a 404.

A common pattern: prerender only the most popular pages at build time, and let the rest render on first visit. This keeps builds fast for large sites.

generateStaticParams runs at build time and returns the params to prerender.
It replaces getStaticPaths from the Pages Router.
With dynamicParams = true (the default), other params render on demand.
With dynamicParams = false, other params return a 404.
Prerender only popular pages to keep builds short.