page-transition-animation

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.

// app/template.tsx
'use client';
import { AnimatePresence } from 'framer-motion';
import

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.

For SPA-style App Router navigations, wrap the router update:

next-view-transitions library

next-view-transitions integrates the View Transitions API with the App Router's client navigation so it works out of the box:

Choose View Transitions for simple cross-page fades/morphs and shared-element transitions with minimal JS; choose Framer Motion when fine-grained, orchestrated, interruptible, or staggered exit animations are needed. View Transitions API browser support is still uneven, so provide a graceful fallback (the if (document.startViewTransition) guard).

AnimatePresence debug checklist

When exit still won't fire, verify in order:

1. Wrapper stays mounted. AnimatePresence must live in something persistent — ideally template.tsx, or a layout-level client component — not inside the page that's unmounting.
2. Stable, changing key. The animated child needs key={pathname} (or similar) so removal is detected. No key, or a key that doesn't change → no exit.
3. Direct motion descendant. The element with the exit prop must be a motion.* component and a child of AnimatePresence (a non-motion wrapper in between can block detection).
4. mode="wait" if old and new should not overlap; without it both render simultaneously and may jump.
5. FrozenRouter present if the outgoing page flashes the new route's content during exit.
6. 'use client' on every file using AnimatePresence/usePathname/motion.
7. Single child at a time under mode="wait" — AnimatePresence expects one keyed presence to swap.

Deliver & verify (standalone HTML)

Packaged helper (scripts/): scripts/seek-shot.sh anim.html 0 1.5 3 freezes the ?t=N harness and screenshots each moment; scripts/contact-sheet.sh sheet.png frame-*.png tiles them for one-glance review. See scripts/README.md.

The real target is a Next.js app, but to prove the transition shape (the enter/exit curve, direction, crossfade) you can ship one HTML file that opens directly in a browser — two stub "pages" you toggle, animated with motion from CDN or the native View Transitions API. One file is the right tier for validating motion before wiring the router; don't stand up Next just to eyeball a fade.

Output contract:

• One .html file: two view stubs and a toggle, animated with either an inline <script type="module"> importing motion/React from CDN, or document.startViewTransition + ::view-transition-* CSS.
• A way to freeze the resolved end state — a route transition is state-driven (which view, mid-swap), so screenshot the state, not a clock.

Seek harness — pin a transition phase. ?view=b mounts the destination view (or ?phase=exit to hold the outgoing tree mid-animation) so a screenshot lands on a settled phase:

Verify loop — render → set phase → screenshot → check: open source, mid, and destination (?view=a, ?phase=exit, ?view=b), screenshot each, and check fidelity (exit actually runs, direction/crossfade matches the brief, no mode="wait" lag) plus artifacts (outgoing tree flashing the new page's content, double-mount, FOUC, jank). Any headless tool works:

Before you finish:

1. Opens standalone — no console errors, CDN motion/React (if used) resolves, startViewTransition guarded.
2. The ?view=/?phase= freeze lands a deterministic transition phase.
3. Screenshotted at source / mid / destination — matches the brief, no content flash or skipped exit.
4. prefers-reduced-motion honored — slide/translate dropped to a short crossfade.
5. Easing is intentional — entrances ease-out, exits ease-in, durations ~0.2–0.4s (not laggy under mode="wait").

Quick reference

Gotchas

• layout.tsx persists and will NOT remount per route — use template.tsx for per-route enter animations.
• Omitting FrozenRouter makes the exiting page render the new route's content mid-animation (visible flash) or skip exit entirely.
• LayoutRouterContext import path is a Next internal; it may change across versions — first thing to fix after an upgrade.
• Without key={pathname}, AnimatePresence sees the same child and never triggers exit.
• mode="wait" waits for exit before enter; overusing it on slow exits makes navigation feel laggy — tune durations (~0.2-0.4s).
• View Transitions API lacks full browser support; always guard document.startViewTransition.
• Every transition file needs 'use client'; server components can't use AnimatePresence/usePathname.

Reference files

• references/full-examples.md — directional/slide transitions, shared-element View Transitions with view-transition-name, a non-mode="wait" crossfade variant, loading-state transitions with loading.tsx, and a complete working App Router folder layout.*