# Page Transition Animation (Next.js App Router)

Implement page enter/exit transitions in the Next.js **App Router**, and fix the single most common failure: **Framer Motion `AnimatePresence` exit animations never fire on navigation**. The reason is structural — in the App Router, when navigating, Next.js unmounts the old route's content and mounts the new one almost immediately. `AnimatePresence` can only animate an exit if the *exiting element stays mounted* under a *persistent* `AnimatePresence` wrapper long enough to run the animation. Because the router swaps children out from under it, the exit is skipped. Two approaches solve this: a pathname-keyed `AnimatePresence` with the **FrozenRouter** pattern, or the **View Transitions API** (native / `next-view-transitions`).

## When to use

Use when adding animated page transitions in a Next.js App Router app, when a Framer Motion `exit` prop does nothing on route change, when an old page disappears instantly instead of animating out, when choosing between Framer Motion and the View Transitions API for Next.js, or when debugging why `AnimatePresence` won't animate between routes.

## Why exit doesn't fire (the core problem)

`AnimatePresence` detects removal of a *direct keyed child*. On App Router navigation:

1. The wrapper must persist across the navigation. If `AnimatePresence` lives in a component that itself unmounts, there is nothing left to run the exit.
2. The child's `key` must change per route so AnimatePresence sees "old removed, new added".
3. During the brief overlap, the *outgoing* subtree must still render its old content — but the App Router has already swapped the route context, so the outgoing tree would otherwise render the *new* page's data. This is what **FrozenRouter** fixes.

## Solution A: template.tsx + keyed AnimatePresence + FrozenRouter

`template.tsx` is the App Router's purpose-built hook for this: unlike `layout.tsx` (which persists), a **template remounts on every navigation**, giving each route a fresh instance — ideal for per-route enter animations. Combine it with a pathname-keyed `AnimatePresence` and FrozenRouter for clean exit + enter.

```tsx
// app/template.tsx
'use client';
import { AnimatePresence } from 'framer-motion';
import { usePathname } from 'next/navigation';
import { FrozenRouter } from './frozen-router';
import { PageTransition } from './page-transition';

export default function Template({ children }: { children: React.ReactNode }) {
  const pathname = usePathname();
  return (
    <AnimatePresence mode="wait" initial={false}>
      {/* key on pathname so AnimatePresence sees old removed / new added */}
      <PageTransition key={pathname}>
        {/* FrozenRouter keeps the OUTGOING tree rendering its old content
            while it animates out */}
        <FrozenRouter>{children}</FrozenRouter>
      </PageTransition>
    </AnimatePresence>
  );
}
```

```tsx
// app/page-transition.tsx
'use client';
import { motion } from 'framer-motion';

export function PageTransition({ children }: { children: React.ReactNode }) {
  return (
    <motion.div
      initial={{ opacity: 0, y: 12 }}
      animate={{ opacity: 1, y: 0 }}
      exit={{ opacity: 0, y: -12 }}
      transition={{ duration: 0.3, ease: [0.22, 1, 0.36, 1] }}
    >
      {children}
    </motion.div>
  );
}
```

```tsx
// app/frozen-router.tsx
'use client';
import { useContext, useRef } from 'react';
import {
  LayoutRouterContext,
} from 'next/dist/shared/lib/app-router-context.shared-runtime';

// Freezes the router context so the exiting page keeps rendering its
// OWN content during the exit animation instead of the next route's.
export function FrozenRouter({ children }: { children: React.ReactNode }) {
  const context = useContext(LayoutRouterContext ?? {});
  const frozen = useRef(context).current;

  return (
    <LayoutRouterContext.Provider value={frozen}>
      {children}
    </LayoutRouterContext.Provider>
  );
}
```

How it fits together:

- `mode="wait"` makes AnimatePresence fully finish the exit before mounting the new page. (Use the default mode if enter/exit should overlap/crossfade.)
- `initial={false}` skips the enter animation on first load (optional).
- `key={pathname}` is what makes AnimatePresence treat each route as a distinct presence.
- `FrozenRouter` snapshots `LayoutRouterContext` so the outgoing subtree renders the *previous* route's content throughout the exit, instead of flashing the new route's content. Without it, exit either skips or shows the wrong content.

Note: `LayoutRouterContext` is a Next.js internal; its import path can change between Next versions. If the import breaks after an upgrade, that path is the thing to update.

## Solution B: native View Transitions API

The View Transitions API animates between two DOM states with the browser capturing before/after snapshots — no per-element exit components.

```css
/* globals.css */
@view-transition { navigation: auto; } /* opt MPA-style in (where supported

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