Next.js 15 Fullstack (App Router + Server Actions) · Lesson

Dynamic Routes & Params

Learn to implement dynamic routes to handle variable segments in URLs and access route parameters.

Dynamic Routes & Params is a free Next.js 15 Fullstack (App Router + Server Actions) lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Next.js 15 Fullstack (App Router + Server Actions) learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

What are Dynamic Routes?

Imagine you have a blog with many posts. Instead of creating a separate page for each post (like /blog/post-1, /blog/post-2), you can use dynamic routes.

Dynamic routes allow you to create pages that respond to variable segments in the URL, making your application scalable and maintainable.

Defining a Basic Dynamic Route

In Next.js App Router, you define a dynamic route segment by wrapping a folder name in square brackets []. For example, to create a dynamic route for blog posts, you'd create a folder named [slug].

app/blog/[slug]/page.js

This structure will match URLs like /blog/first-post, /blog/another-article, etc.

Accessing Route Parameters

When a dynamic route is matched, the variable part of the URL becomes available as a route parameter. You can access these parameters within your page component via the params prop.

For app/blog/[slug]/page.js, the URL /blog/my-first-post would make params.slug equal to 'my-first-post'.

Demo: Simple Dynamic Page

Let's see how to create a simple dynamic page that displays the slug parameter from the URL. Place this code in app/blog/[slug]/page.js.

export default function BlogPostPage({ params }) {
  // params.slug will contain the dynamic part of the URL
  return (
    <div>
      <h1>Blog Post: {params.slug}</h1>
      <p>This content is dynamically loaded!</p>
    </div>
  );
}

Understanding Catch-all Segments

What if you need to match a path with an unknown number of segments? This is where catch-all segments come in handy. You define them using a spread syntax: [...slug].

app/docs/[...slug]/page.js

This will match URLs like /docs/a, /docs/a/b, /docs/a/b/c, etc.

Accessing Catch-all Parameters

When using a catch-all segment, the params prop will contain an array of the matched segments. So, for app/docs/[...slug]/page.js:

/docs/a -> params.slug is ['a']
/docs/a/b/c -> params.slug is ['a', 'b', 'c']

Demo: Catch-all Page

Here's how you can display all segments from a catch-all route. Place this code in app/docs/[...slug]/page.js.

export default function DocsPage({ params }) {
  // params.slug is an array of path segments
  const path = params.slug.join('/');
  return (
    <div>
      <h1>Documentation Path: /{path}</h1>
      <p>Showing content for: {path}</p>
    </div>
  );
}

Optional Catch-all Segments

Sometimes you want a catch-all segment that can also match the base path (i.e., zero segments). This is an optional catch-all, defined with double square brackets: [[...slug]].

app/users/[[...id]]/page.js

This will match /users (where params.id is undefined) AND /users/123 (where params.id is ['123']).

Demo: Optional Catch-all

This example shows an optional catch-all route that displays a user ID or 'Guest' if no ID is provided. Place this in app/users/[[...id]]/page.js.

export default function UserProfilePage({ params }) {
  // params.id will be undefined for /users, or ['123'] for /users/123
  const userId = params.id ? params.id[0] : 'Guest';
  return (
    <div>
      <h1>Welcome, {userId}</h1>
      <p>This page handles both base and dynamic paths.</p>
    </div>
  );
}

Dynamic Routes Quiz

Which of the following file structures would allow a Next.js App Router application to handle URLs like /products/electronics/laptops and access 'electronics' and 'laptops' separately?

Recap: Dynamic Routes & Params

Great job! You've learned the essentials of dynamic routing in Next.js App Router:

[slug] creates a single dynamic segment.
[...slug] creates a catch-all segment for multiple paths, returning an array.
[[...slug]] creates an optional catch-all, matching zero or more segments.
All dynamic segments are accessed via the params prop in your page.js components.

This powerful feature is key for building flexible and scalable web applications!

Frequently asked questions

Is the “Dynamic Routes & Params” lesson free?

Yes — the full text of “Dynamic Routes & Params” is free to read here on the web, and the Next.js 15 Fullstack (App Router + Server Actions) course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Next.js 15 Fullstack (App Router + Server Actions) course, upgrade to CoddyKit PRO.

What will I learn in “Dynamic Routes & Params”?

Learn to implement dynamic routes to handle variable segments in URLs and access route parameters. You practise Next.js 15 Fullstack (App Router + Server Actions) with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Next.js 15 Fullstack (App Router + Server Actions)?

No prior experience is required. Next.js 15 Fullstack (App Router + Server Actions) on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Dynamic Routes & Params” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Next.js 15 Fullstack (App Router + Server Actions) lesson?

Yes. Every Next.js 15 Fullstack (App Router + Server Actions) lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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