Declare a dynamic route

A dynamic segment lets one page template represent several URLs.

src/pages/posts/[slug].astro

The bracket name becomes a route parameter. A request for /posts/hello-astro/ has a slug value of hello-astro.

Inside the page:

---
const { slug } = Astro.params
---

<h1>Post: {slug}</h1>

The parameter tells you which route matched. It is still input. Validate it before using it in a database query, file path, or authorization decision.

Rendering mode changes how the value becomes available. A static project needs the complete set of slugs during the build, provided by getStaticPaths(). An on-demand route can receive the current request parameter at runtime but needs a compatible adapter.

Use [...slug].astro for a rest parameter that can match several path segments. Choose it only when nested paths are part of the content model.

Create one dynamic route and try a known and unknown value. Decide whether the unknown path should be built, return a 404, or be handled on demand.