Next.js Dynamic Route Params Await Issue

Problem: Async Dynamic Route Params Access in Next.js

When implementing dynamic route localization in Next.js 15 using the App Router, developers commonly encounter the error:

shell

Error: Route "/[locale]" used `params.locale`. `params` should be awaited before using its properties

This occurs when attempting to access route parameters (params.locale) in your dynamic route files without properly awaiting the asynchronous params object.

Core symptoms include:

Error persists even after properly destructuring params
Using generateStaticParams() doesn't resolve the issue
Type declarations appear correct but error remains
Occurs specifically in layout.tsx/page.tsx in dynamic route segments (app/[locale]/)

In Next.js 15, several APIs including route parameters became asynchronous to support advanced use cases. Let's explore how to properly handle this.

Key Change in Next.js 15

Dynamic APIs like params now return promises rather than static values. All route parameters should be treated as asynchronous resources.

Solutions: Accessing Async Route Params

1. Await Promise-Based Params (Recommended)

tsx

import { ReactNode } from 'react';
import i18nConfig from '@/i18nConfig';

// Declare params as Promise type
interface RootLayoutProps {
  children: ReactNode;
  params: Promise<{ locale: string }>;
}

export default async function RootLayout({ 
  children,
  params 
}: RootLayoutProps) {
  // Await params before accessing properties
  const { locale } = await params;
  
  return (
    <html lang={locale}>  
      <body>{children}</body>
    </html>
  );
}

Why this works:

Explicitly types params as Promise<{ locale: string }>
await resolves the promise before accessing values
Maintains full compatibility with App Router features
Works in both layout.tsx and page.tsx files

Same Fix for Page Components

Apply identical promise handling in page.tsx:

tsx

export default async function Home({
  params
}: {
  params: Promise<{ locale: string }>;
}) {
  const { locale } = await params;
  
  return <main>Locale: {locale}</main>;
}

2. Resolve Static Asset Conflict (Alternative Fix)

diff

app/
├── [locale]/
│   ├── layout.tsx
│   ├── page.tsx
│   └── ✗ icon.png   // Remove static files
├── ✓ icon.png        // Move to root app directory
locales/

Why this works:

Next.js interprets files in dynamic route directories as potential routes
Static assets like PNG/ICO files falsely trigger dynamic routing handlers
Moving them out of [locale]/ prevents false route matching

3. Use Codemod for Automated Migration

shell

npx @next/codemod@canary next-async-request-api

Benefits:

Automatically updates code patterns
Handles edge cases consistently
Follows Vercel's official migration path (see docs)

Understanding the Architecture Change

Next.js 15 introduced significant changes to dynamic routing APIs:

Concept	Pre-Next.js 15	Next.js 15+
`params`	Synchronous object	Async/Promise-based
Access method	Direct property access	Requires `await`
Error handling	No async warnings	Explicit errors

The change enables dynamic parameter resolution during rendering, supporting:

Database-driven route segments
Runtime configuration
Internationalized routing at render-time
Hybrid static/dynamic rendering strategies

Common Pitfalls

Incorrect handling in server actions:

export async function POST(req, { params }) {
  const { id } = await params;  // Required!
}

Legacy API compatibility: Middleware still receives synchronous params

Best Practices for Async Routing

Always type with Promise:
ts
```
params: Promise<{ slug: string }>
```

Destructure after awaiting:

// ✅ Correct
const { slug } = await params;

// ❌ Avoid
const slug = (await params).slug;

Combine with generateStaticParams:

export function generateStaticParams() {
  return [{ locale: 'en' }, { locale: 'lt' }];
}

By following these patterns, you'll build Next.js applications that fully leverage the App Router's capabilities while avoiding common async routing pitfalls.

Related Posts

Next.js Dynamic Route Params Await Issue ​

Problem: Async Dynamic Route Params Access in Next.js ​

Solutions: Accessing Async Route Params ​

1. Await Promise-Based Params (Recommended) ​

2. Resolve Static Asset Conflict (Alternative Fix) ​

3. Use Codemod for Automated Migration ​

Understanding the Architecture Change ​

Best Practices for Async Routing ​