Next.js Dynamic Routes and Pathname Parameters

When to Use This Skill

Use this skill when:

Creating dynamic route segments (e.g., blog/[slug], users/[id])
Accessing URL pathname parameters in Server or Client Components
Building pages that fetch data based on route parameters
Implementing catch-all or optional catch-all routes
Working with the
```
params
```
prop in page.tsx, layout.tsx, or route.ts

⚠️ RECOGNIZING WHEN YOU NEED DYNAMIC ROUTES

Look for requirements that tie data to the URL path.

Create a dynamic segment (

[param]

) whenever the UI depends on part of the pathname. Typical signals include:

Details pages that reference “the item’s ID/slug from the URL”
Copy that calls out path segments (e.g.,
```
/products/{id}
```
,
```
/blog/{slug}
```
)
Requirements to fetch data “based on whichever resource is being visited”
Navigation flows where one page links to
```
/something/{identifier}
```

✅ Dynamic route response

Requirement: display product information based on whichever ID appears in the URL
Implementation: app/[id]/page.tsx
Access parameter with: const { id } = await params;

❌ Static-page response

Implementation: app/page.tsx  ← cannot access per-path identifiers

Example requirements that lead to dynamic routes

“Show a product page that loads whichever product ID appears in the URL” →
```
app/[id]/page.tsx
```
or
```
app/products/[id]/page.tsx
```
“Render a blog article based on its slug” →
```
app/blog/[slug]/page.tsx
```
or
```
app/[slug]/page.tsx
```
“Support nested docs such as /docs/getting-started/installation” →
```
app/docs/[...slug]/page.tsx
```

Core rule: If data varies with a URL segment, the folder name needs matching brackets.

⚠️ CRITICAL: Avoid Over-Engineering Route Structure

MOST COMMON MISTAKE: Adding unnecessary nesting to routes.

Default Rule: When creating a dynamic route, use

app/[id]/page.tsx

app/[slug]/page.tsx

unless:

The URL structure is explicitly specified (e.g., "create route at /products/[id]")
You're building multiple resource types that need namespacing
The requirements clearly show a nested URL structure

Do NOT infer nesting from resource names:

"Fetch a product by ID" →
```
app/[id]/page.tsx
```
✅ (not
```
app/products/[id]
```
)
"Show user profile" →
```
app/[userId]/page.tsx
```
✅ (not
```
app/users/[userId]
```
)
"Display blog post" →
```
app/[slug]/page.tsx
```
✅ (not
```
app/blog/[slug]
```
)

Only nest when explicitly told:

"Create a route at /blog/[slug]" →
```
app/blog/[slug]/page.tsx
```
✅
"Products should be at /products/[id]" →
```
app/products/[id]/page.tsx
```
✅

Core Concepts

Dynamic Route Syntax

Next.js uses folder names with square brackets to create dynamic route segments:

app/
├── [id]/page.tsx              # Matches /123, /abc, etc.
├── blog/[slug]/page.tsx       # Matches /blog/hello-world
├── shop/[category]/[id]/page.tsx  # Matches /shop/electronics/123
└── docs/[...slug]/page.tsx    # Matches /docs/a, /docs/a/b, /docs/a/b/c

Key Principle: The folder structure IS the route structure.

Route Structure Decision Tree

CRITICAL RULE: Do NOT infer route structure from resource type names!

Just because you're fetching a "product" or "user" doesn't mean you need

/products/[id]

/users/[id]

. Unless explicitly told otherwise, prefer the simplest structure.

When deciding on route structure:

Top-level dynamic route (
```
app/[id]/page.tsx
```
)
- DEFAULT CHOICE - Use this unless specifically told otherwise
- Use when the resource IS the primary entity
- Use when only ID-based routing is needed
- Examples:
```
/123
```
  for any resource,
```
/abc-def
```
  for slugs
- Pattern: The ID/slug is the only identifier needed
- When in doubt, choose this!
Nested dynamic route (
```
app/category/[id]/page.tsx
```
)
- ONLY use when explicitly required by the URL structure
- Use when you're told "create a /products/[id] route"
- Use when the URL itself needs the category prefix
- Examples:
```
/products/123
```
  ,
```
/blog/my-post
```
  (when specified)
- Pattern: Category + identifier (when both are required)
Multi-segment dynamic (
```
app/[cat]/[id]/page.tsx
```
)
- Use when hierarchy matters
- Examples:
```
/shop/electronics/123
```
- Pattern: Multiple levels of categorization

⚠️ COMMON MISTAKE: Creating

app/products/[id]/page.tsx

when you should create

app/[id]/page.tsx

❌ WRONG: "Fetch a product by ID" →

app/products/[id]/page.tsx

✅ CORRECT: "Fetch a product by ID" →

app/[id]/page.tsx

❌ WRONG: "Create a dynamic route for users" →

app/users/[userId]/page.tsx

✅ CORRECT: "Create a dynamic route for users" →

app/[userId]/page.tsx

Only add the category prefix when:

The requirement explicitly says "at /products/..." or similar
You're building multiple resource types that need namespacing
The URL structure is specified in requirements

Accessing Pathname Parameters

In Server Components (page.tsx, layout.tsx)

CRITICAL: In Next.js 15+,
params
is a Promise and must be awaited!

typescript

// ✅ CORRECT - Next.js 15+
export default async function ProductPage({
  params,
}: {
  params: Promise<{ id: string }>;
}) {
  const { id } = await params;

  const product = await fetch(`https://api.example.com/products/${id}`)
    .then(res => res.json());

  return <div>{product.name}</div>;
}

typescript

// ❌ WRONG - Treating params as synchronous object (Next.js 15+)
export default async function ProductPage({
  params,
}: {
  params: { id: string };  // Missing Promise wrapper
}) {
  const product = await fetch(`https://api.example.com/products/${params.id}`);
  // This will fail because params is a Promise!
}

For Next.js 14 and earlier:

typescript

// Next.js 14 - params is synchronous
export default async function ProductPage({
  params,
}: {
  params: { id: string };
}) {
  const product = await fetch(`https://api.example.com/products/${params.id}`)
    .then(res => res.json());

  return <div>{product.name}</div>;
}

In Route Handlers (route.ts)

typescript

// app/api/products/[id]/route.ts
export async function GET(
  request: Request,
  { params }: { params: Promise<{ id: string }> }
) {
  const { id } = await params;

  const product = await db.products.findById(id);
  return Response.json(product);
}

In Client Components

You CANNOT access
params
directly in Client Components. Instead:

Use
useParams()
hook:

typescript

'use client';

import { useParams } from 'next/navigation';

export function ProductClient() {
  const params = useParams<{ id: string }>();
  const id = params.id;

  // Use the id...
}

Pass params from Server Component:

typescript

// app/products/[id]/page.tsx (Server Component)
export default async function ProductPage({
  params,
}: {
  params: Promise<{ id: string }>;
}) {
  const { id } = await params;
  return <ProductClient productId={id} />;
}

// components/ProductClient.tsx
'use client';

export function ProductClient({ productId }: { productId: string }) {
  // Use productId...
}

Common Patterns

Pattern 1: Simple ID-Based Page

typescript

// app/[id]/page.tsx - Top-level dynamic route
interface PageProps {
  params: Promise<{ id: string }>;
}

export default async function ItemPage({ params }: PageProps) {
  const { id } = await params;

  const item = await fetch(`https://api.example.com/items/${id}`)
    .then(res => res.json());

  return (
    <div>
      <h1>{item.title}</h1>
      <p>{item.description}</p>
    </div>
  );
}

Pattern 2: Blog Post with Slug

typescript

// app/blog/[slug]/page.tsx
interface PageProps {
  params: Promise<{ slug: string }>;
}

export default async function BlogPost({ params }: PageProps) {
  const { slug } = await params;

  const post = await getPostBySlug(slug);

  return (
    <article>
      <h1>{post.title}</h1>
      <div dangerouslySetInnerHTML={{ __html: post.content }} />
    </article>
  );
}

// Generate static params for SSG
export async function generateStaticParams() {
  const posts = await getAllPosts();

  return posts.map((post) => ({
    slug: post.slug,
  }));
}

Pattern 3: Nested Resources

typescript

// app/users/[userId]/posts/[postId]/page.tsx
interface PageProps {
  params: Promise<{
    userId: string;
    postId: string;
  }>;
}

export default async function UserPost({ params }: PageProps) {
  const { userId, postId } = await params;

  const [user, post] = await Promise.all([
    getUserById(userId),
    getPostById(postId),
  ]);

  return (
    <div>
      <h1>{post.title}</h1>
      <p>By {user.name}</p>
      <div>{post.content}</div>
    </div>
  );
}

Pattern 4: Catch-All Routes

typescript

// app/docs/[...slug]/page.tsx - Matches /docs/a, /docs/a/b, /docs/a/b/c
interface PageProps {
  params: Promise<{
    slug: string[];  // Array of path segments
  }>;
}

export default async function DocsPage({ params }: PageProps) {
  const { slug } = await params;
  const path = slug.join('/');

  const doc = await getDocByPath(path);

  return <div>{doc.content}</div>;
}

typescript

// app/shop/[[...slug]]/page.tsx - Optional catch-all
// Matches /shop, /shop/electronics, /shop/electronics/phones
interface PageProps {
  params: Promise<{
    slug?: string[];  // Optional array
  }>;
}

export default async function ShopPage({ params }: PageProps) {
  const { slug = [] } = await params;

  if (slug.length === 0) {
    return <ShopHomepage />;
  }

  return <CategoryPage category={slug.join('/')} />;
}

TypeScript Best Practices

Type Safety for Params

typescript

// Define params type separately for reusability
type ProductPageParams = { id: string };

interface ProductPageProps {
  params: Promise<ProductPageParams>;
}

export default async function ProductPage({ params }: ProductPageProps) {
  const { id } = await params;
  // id is typed as string
}

// Reuse in generateMetadata
export async function generateMetadata({ params }: ProductPageProps) {
  const { id } = await params;
  const product = await getProduct(id);
  return { title: product.name };
}

Multiple Dynamic Segments

typescript

type PostPageParams = {
  category: string;
  slug: string;
};

interface PostPageProps {
  params: Promise<PostPageParams>;
  searchParams: Promise<{ [key: string]: string | string[] | undefined }>;
}

export default async function PostPage({ params, searchParams }: PostPageProps) {
  const { category, slug } = await params;
  const { view } = await searchParams;

  // All properly typed
}

Common Pitfalls and Solutions

Pitfall 1: Forgetting params is a Promise (Next.js 15+)

typescript

// ❌ WRONG
export default async function Page({ params }: { params: { id: string } }) {
  const product = await getProduct(params.id);  // Error: params is Promise
}

// ✅ CORRECT
export default async function Page({ params }: { params: Promise<{ id: string }> }) {
  const { id } = await params;
  const product = await getProduct(id);
}

Pitfall 2: Using params in Client Components without useParams

typescript

// ❌ WRONG - params prop doesn't exist in Client Components
'use client';

export default function ClientPage({ params }) {  // undefined!
  return <div>{params.id}</div>;
}

// ✅ CORRECT
'use client';
import { useParams } from 'next/navigation';

export default function ClientPage() {
  const params = useParams<{ id: string }>();
  return <div>{params.id}</div>;
}

Pitfall 3: Over-nesting Routes

typescript

// ❌ UNNECESSARY NESTING
// app/products/product/[id]/page.tsx
// URL: /products/product/123

// ✅ SIMPLER
// app/products/[id]/page.tsx
// URL: /products/123

// OR even simpler if product is the main resource:
// app/[id]/page.tsx
// URL: /123

Pitfall 4: Not Handling Invalid IDs

typescript

// ✅ ROBUST
export default async function ProductPage({
  params,
}: {
  params: Promise<{ id: string }>;
}) {
  const { id } = await params;

  const product = await fetch(`https://api.example.com/products/${id}`)
    .then(res => {
      if (!res.ok) throw new Error('Product not found');
      return res.json();
    });

  if (!product) {
    notFound();  // Shows 404 page
  }

  return <div>{product.name}</div>;
}

Decision Guide

When you need to create a dynamic route, ask:

What's the URL structure?
- Single ID:
```
[id]
```
- Category + ID:
```
category/[id]
```
- Hierarchical:
```
[category]/[id]
```
- Flexible paths:
```
[...slug]
```
Is this a Server or Client Component?
- Server: Use
```
params
```
  prop (await it in Next.js 15+)
- Client: Use
```
useParams()
```
  hook
Do I need the simplest structure?
- When in doubt, use fewer nesting levels
- Top-level routes are simpler and more direct
Am I on Next.js 15+?
- Yes:
```
params
```
  is
```
Promise<{...}>
```
- No:
```
params
```
  is
```
{...}
```

Examples: Real-World Scenarios

E-commerce Product Page

typescript

// app/products/[id]/page.tsx
import { notFound } from 'next/navigation';

interface Product {
  id: string;
  name: string;
  price: number;
  description: string;
}

async function getProduct(id: string): Promise<Product | null> {
  const res = await fetch(`https://api.example.com/products/${id}`, {
    next: { revalidate: 60 },  // Revalidate every 60s
  });

  if (!res.ok) return null;
  return res.json();
}

export default async function ProductPage({
  params,
}: {
  params: Promise<{ id: string }>;
}) {
  const { id } = await params;
  const product = await getProduct(id);

  if (!product) {
    notFound();
  }

  return (
    <div>
      <h1>{product.name}</h1>
      <p>${product.price}</p>
      <p>{product.description}</p>
    </div>
  );
}

export async function generateMetadata({
  params,
}: {
  params: Promise<{ id: string }>;
}) {
  const { id } = await params;
  const product = await getProduct(id);

  return {
    title: product?.name ?? 'Product Not Found',
    description: product?.description,
  };
}

Documentation Site with Nested Paths

typescript

// app/docs/[...slug]/page.tsx
interface DocPageProps {
  params: Promise<{ slug: string[] }>;
}

export default async function DocPage({ params }: DocPageProps) {
  const { slug } = await params;
  const path = slug.join('/');

  const doc = await getDocByPath(path);

  if (!doc) {
    notFound();
  }

  return (
    <article className="prose">
      <h1>{doc.title}</h1>
      <div dangerouslySetInnerHTML={{ __html: doc.html }} />
    </article>
  );
}

export async function generateStaticParams() {
  const docs = await getAllDocs();

  return docs.map((doc) => ({
    slug: doc.path.split('/'),
  }));
}

Checklist for Dynamic Routes

Before implementing a dynamic route, verify:

Route structure is as simple as possible (default to top-level unless told otherwise)
Not inferring route nesting from resource type names
Route structure matches URL requirements (not over-nested)
```
params
```
is typed as
```
Promise<{...}>
```
for Next.js 15+
```
params
```
is awaited before accessing properties (Next.js 15+)
Error handling for invalid IDs/slugs (use
```
notFound()
```
)
TypeScript types are properly defined
Using Server Component unless client interactivity needed
Consider
```
generateStaticParams()
```
for SSG if applicable
Metadata generation if SEO matters

Quick Reference

Scenario	Route Structure	Params Access
Single resource by ID	`app/[id]/page.tsx`	`const { id } = await params`
Category + resource	`app/category/[id]/page.tsx`	`const { id } = await params`
Blog with slugs	`app/blog/[slug]/page.tsx`	`const { slug } = await params`
Nested resources	`app/[cat]/[id]/page.tsx`	`const { cat, id } = await params`
Flexible paths	`app/docs/[...slug]/page.tsx`	`const { slug } = await params` (slug is array)
Optional paths	`app/[[...slug]]/page.tsx`	`const { slug = [] } = await params`
Client Component	Use `useParams()` hook	`const params = useParams<{ id: string }>()`

Remember: Dynamic routes in Next.js are file-system based. The folder structure with

[brackets]

creates the dynamic segments, and the

params

prop (or

useParams()

hook) provides access to those values.

nextjs-dynamic-routes-params

NPX Install

Tags

SKILL.md Content

Next.js Dynamic Routes and Pathname Parameters

When to Use This Skill

⚠️ RECOGNIZING WHEN YOU NEED DYNAMIC ROUTES

⚠️ CRITICAL: Avoid Over-Engineering Route Structure

Core Concepts

Dynamic Route Syntax

Route Structure Decision Tree

Accessing Pathname Parameters

In Server Components (page.tsx, layout.tsx)

In Route Handlers (route.ts)

In Client Components

Common Patterns

Pattern 1: Simple ID-Based Page

Pattern 2: Blog Post with Slug

Pattern 3: Nested Resources

Pattern 4: Catch-All Routes

TypeScript Best Practices

Type Safety for Params

Multiple Dynamic Segments

Common Pitfalls and Solutions

Pitfall 1: Forgetting params is a Promise (Next.js 15+)

Pitfall 2: Using params in Client Components without useParams

Pitfall 3: Over-nesting Routes

Pitfall 4: Not Handling Invalid IDs

Decision Guide

Examples: Real-World Scenarios

E-commerce Product Page

Documentation Site with Nested Paths

Checklist for Dynamic Routes

Quick Reference