Dynamic Routes

When you don't know the exact segment names ahead of time and want to create routes from dynamic data, you can use Dynamic Segments that are filled in at request time or prerendered at build time.

Convention

A Dynamic Segment can be created by wrapping a folder's name in square brackets: [folderName]. For example, [id] or [slug].

Dynamic Segments are passed as the params prop to layout, page, route, and generateMetadata functions.

Example

For example, a blog could include the following route app/blog/[slug]/page.js where [slug] is the Dynamic Segment for blog posts.

export default function Page({ params }: { params: { slug: string } }) {
  return <div>My Post: {params.slug}</div>
}

See the generateStaticParams() page to learn how to generate the params for the segment.

Good to know: Dynamic Segments are equivalent to Dynamic Routes in the pages directory.

Generating Static Params

The generateStaticParams function can be used in combination with dynamic route segments to statically generate routes at build time instead of on-demand at request time.

export async function generateStaticParams() {
  const posts = await fetch('https://.../posts').then((res) => res.json())
 
  return posts.map((post) => ({
    slug: post.slug,
  }))
}

The primary benefit of the generateStaticParams function is its smart retrieval of data. If content is fetched within the generateStaticParams function using a fetch request, the requests are automatically memoized. This means a fetch request with the same arguments across multiple generateStaticParams, Layouts, and Pages will only be made once, which decreases build times.

Use the migration guide if you are migrating from the pages directory.

See generateStaticParams server function documentation for more information and advanced use cases.

Catch-all Segments

Dynamic Segments can be extended to catch-all subsequent segments by adding an ellipsis inside the brackets [...folderName].

For example, app/shop/[...slug]/page.js will match /shop/clothes, but also /shop/clothes/tops, /shop/clothes/tops/t-shirts, and so on.

Optional Catch-all Segments

Catch-all Segments can be made optional by including the parameter in double square brackets: [[...folderName]].

For example, app/shop/[[...slug]]/page.js will also match /shop, in addition to /shop/clothes, /shop/clothes/tops, /shop/clothes/tops/t-shirts.

The difference between catch-all and optional catch-all segments is that with optional, the route without the parameter is also matched (/shop in the example above).

TypeScript

When using TypeScript, you can add types for params depending on your configured route segment.

export default function Page({ params }: { params: { slug: string } }) {
  return <h1>My Page</h1>
}

Good to know: This may be done automatically by the TypeScript plugin in the future.