# Creating custom fallback pages in v0
- Tool: V0
- Difficulty: Intermediate
- Fix time: 15-25 minutes
- Compatibility: V0 with Next.js App Router, TypeScript
- Last updated: March 2026
## TL;DR
Custom fallback pages in V0's Next.js App Router use the not-found.tsx, error.tsx, and catch-all route conventions. Create app/not-found.tsx for 404 pages, app/error.tsx for runtime error boundaries, and app/[...slug]/page.tsx for catch-all routes. Unlike the similar 404 styling page, this guide covers error boundaries and catch-all route patterns that handle unexpected paths gracefully across your entire application.
## Why fallback pages are missing or broken in V0 projects
V0 generates the pages you request but does not automatically create error boundaries, 404 handlers, or catch-all routes. When a user navigates to a non-existent path, Next.js shows its default error page, which has no styling and no navigation back to your app. Without proper error boundaries, a runtime error in one component crashes the entire page instead of showing a recoverable error message. These fallback patterns are essential for production apps but are consistently missing from V0-generated projects.
- V0 does not generate not-found.tsx or error.tsx files unless explicitly prompted
- Catch-all routes need the [...slug] directory naming convention that V0 may not create automatically
- Error boundaries require 'use client' directive — they cannot be Server Components in Next.js
- Nested layouts may not have their own error.tsx, causing errors to bubble up to the root
- V0-generated dynamic routes missing validation, leading to unhandled parameter values
## Error messages you might see
**Error occurred prerendering page "/not-found"**
The not-found.tsx file has a build error, often caused by importing client-only code without the 'use client' directive.
**Application error: a client-side exception has occurred (see the browser console for more information)**
Next.js default error boundary message. This appears when no custom error.tsx exists and a runtime error occurs.
**404 | This page could not be found.**
The default Next.js 404 page. Replace it with a custom not-found.tsx in your app/ directory.
## Before you start
- A V0 project with multiple pages or dynamic routes
- Understanding of Next.js App Router file conventions
- Access to the V0 code editor
## How to fix it
### 1. Create a global not-found.tsx page
*The root-level not-found.tsx handles all unmatched routes in your application, replacing the unstyled default Next.js 404 page.*
Create app/not-found.tsx with your branded 404 content. This file can be a Server Component (no 'use client' needed) unless it uses interactive elements. Include navigation back to the home page.
Before:
```
// No not-found.tsx exists — users see unstyled "404 | This page could not be found."
```
After:
```
// app/not-found.tsx
import Link from 'next/link';
import { Button } from '@/components/ui/button';
export default function NotFound() {
return (
404
This page does not exist.
);
}
```
**Expected result:** Navigating to any non-existent route shows your branded 404 page with a link back to the home page.
### 2. Add a client-side error boundary with error.tsx
*error.tsx catches runtime JavaScript errors in child components and displays a recovery UI instead of crashing the entire page. It must be a client component.*
Create app/error.tsx with the 'use client' directive. It receives error and reset props that let users retry the failed operation.
Before:
```
// No error.tsx — runtime errors show: "Application error: a client-side exception has occurred"
```
After:
```
// app/error.tsx
'use client';
import { useEffect } from 'react';
import { Button } from '@/components/ui/button';
export default function Error({
error,
reset,
}: {
error: Error & { digest?: string };
reset: () => void;
}) {
useEffect(() => {
console.error('Application error:', error);
}, [error]);
return (
Something went wrong
An unexpected error occurred.
);
}
```
**Expected result:** Runtime errors show a styled error page with a Try Again button instead of crashing the application.
### 3. Create a catch-all route for custom path handling
*Catch-all routes intercept any URL path and let you validate, redirect, or render custom content. This is useful for migrated sites, CMS-driven pages, or vanity URLs.*
Create app/[...slug]/page.tsx to match any path segment combination. Validate the slug and either render content or call notFound() to trigger the 404 page.
Before:
```
// Unmatched routes fall through to the default 404
```
After:
```
// app/[...slug]/page.tsx
import { notFound } from 'next/navigation';
const validPages: Record = {
'about/team': { title: 'Our Team', content: 'Meet the team.' },
'about/mission': { title: 'Our Mission', content: 'Our mission statement.' },
};
export default function CatchAllPage({
params,
}: {
params: { slug: string[] };
}) {
const path = params.slug.join('/');
const page = validPages[path];
if (!page) notFound();
return (
{page.title}
{page.content}
);
}
```
**Expected result:** Valid paths like /about/team render custom content. Invalid paths trigger the not-found.tsx page.
### 4. Add nested error boundaries for route groups
*A single root error.tsx catches all errors. Adding error.tsx to specific route directories creates isolated error boundaries so one section's failure does not affect others.*
Create error.tsx files in route directories that have independent error handling needs, such as app/dashboard/error.tsx for the dashboard section. For projects with many independent sections, RapidDev can help design an error boundary architecture that matches your application's structure.
Before:
```
// Only app/error.tsx exists — all errors show the same UI
```
After:
```
// app/dashboard/error.tsx
'use client';
import { Button } from '@/components/ui/button';
import Link from 'next/link';
export default function DashboardError({
error,
reset,
}: {
error: Error;
reset: () => void;
}) {
return (
Dashboard Error
Could not load dashboard data.
);
}
```
**Expected result:** Dashboard errors show a dashboard-specific error message while the rest of the application continues working.
## Complete code example
File: `app/not-found.tsx`
```tsx
import Link from 'next/link';
import { Button } from '@/components/ui/button';
import { FileQuestion } from 'lucide-react';
export default function NotFound() {
return (
Page Not Found
The page you are looking for does not exist or has been moved.