--- description: "Guide React and Next.js view transitions, shared element animations, route transitions, transition types, and reduced-motion-safe UI state animation." --- # React View Transitions Animate between UI states using the browser's native `document.startViewTransition`. Declare *what* with `<ViewTransition>`, trigger *when* with `startTransition` / `useDeferredValue` / `Suspense`, control *how* with CSS classes. Unsupported browsers skip animations gracefully. ## When to Use - Use this skill when the task matches this description: Guide React and Next.js view transitions, shared element animations, route transitions, transition types, and reduced-motion-safe UI state animation. ## When to Animate Every `<ViewTransition>` should communicate a spatial relationship or continuity. If you can't articulate what it communicates, don't add it. Implement **all** applicable patterns from this list, in this order: | Priority | Pattern | What it communicates | |----------|---------|---------------------| | 1 | **Shared element** (`name`) | "Same thing — going deeper" | | 2 | **Suspense reveal** | "Data loaded" | | 3 | **List identity** (per-item `key`) | "Same items, new arrangement" | | 4 | **State change** (`enter`/`exit`) | "Something appeared/disappeared" | | 5 | **Route change** (layout-level) | "Going to a new place" | This is an implementation order, not a "pick one" list. Implement every pattern that fits the app. Only skip a pattern if the app has no use case for it. ### Choosing Animation Style | Context | Animation | Why | |---------|-----------|-----| | Hierarchical navigation (list → detail) | Type-keyed `nav-forward` / `nav-back` | Communicates spatial depth | | Lateral navigation (tab-to-tab) | Bare `<ViewTransition>` (fade) or `default="none"` | No depth to communicate | | Suspense reveal | `enter`/`exit` string props | Content arriving | | Revalidation / background refresh | `default="none"` | Silent — no animation needed | Reserve directional slides for hierarchical navigation (list → detail) and ordered sequences (prev/next photo, carousel, paginated results). For ordered sequences, the direction communicates position: "next" slides from right, "previous" from left. Lateral/unordered navigation (tab-to-tab) should not use directional slides — it falsely implies spatial depth. --- ## Availability - **Next.js:** Do **not** install `react@canary` — the App Router already bundles React canary internally. `ViewTransition` works out of the box. `npm ls react` may show a stable-looking version; this is expected. - **Without Next.js:** Install `react@canary react-dom@canary` (`ViewTransition` is not in stable React). - Browser support: Chromium 111+, Firefox 144+, Safari 18.2+. Graceful degradation on unsupported browsers. --- ## Implementation Workflow When adding view transitions to an existing app, **follow `references/implementation.md` step by step.** Start with the audit — do not skip it. Copy the CSS recipes from `references/css-recipes.md` into the global stylesheet — do not write your own animation CSS. --- ## Core Concepts ### The `<ViewTransition>` Component ```jsx import { ViewTransition } from 'react'; <ViewTransition> <Component /> </ViewTransition> ``` React auto-assigns a unique `view-transition-name` and calls `document.startViewTransition` behind the scenes. Never call `startViewTransition` yourself. ### Animation Triggers | Trigger | When it fires | |---------|--------------| | **enter** | `<ViewTransition>` first inserted during a Transition | | **exit** | `<ViewTransition>` first removed during a Transition | | **update** | DOM mutations inside a `<ViewTransition>`. With nested VTs, mutation applies to the innermost one | | **share** | Named VT unmounts and another with same `name` mounts in the same Transition | Only `startTransition`, `useDeferredValue`, or `Suspense` activate VTs. Regular `setState` does not animate. ### Critical Placement Rule `<ViewTransition>` only activates enter/exit if it appears **before any DOM nodes**: ```jsx // Works <ViewTransition enter="auto" exit="auto"> <div>Content</div> </ViewTransition> // Broken — div wraps the VT, suppressing enter/exit <div> <ViewTransition enter="auto" exit="auto"> <div>Content</div> </ViewTransition> </div> ``` --- ## Styling with View Transition Classes ### Props Values: `"auto"` (browser cross-fade), `"none"` (disabled), `"class-name"` (custom CSS), or `{ [type]: value }` for type-specific animations. ```jsx <ViewTransition default="none" enter="slide-in" exit="slide-out" share="morph" /> ``` If `default` is `"none"`, all triggers are off unless explicitly listed. ### CSS Pseudo-Elements - `::view-transition-old(.class)` — outgoing snapshot - `::view-transition-new(.class)` — incoming snapshot - `::view-transition-group(.class)` — container - `::view-transition-image-pair(.class)` — old + new pair See `references/css-recipes.md` for ready-to-use animation recipes. --- ## Transition Types Tag transitions with `addTransitionType` so VTs can pick different animations based on context. Call it multiple times to stack types — different VTs in the tree react to different types: ```jsx startTransition(() => { addTransitionType('nav-forward'); addTransitionType('select-item'); router.push('/detail/1'); }); ``` Pass an object to map types to CSS classes. Works on `enter`, `exit`, **and** `share`: ```jsx <ViewTransition enter={{ 'nav-forward': 'slide-from-right', 'nav-back': 'slide-from-left', default: 'none' }} exit={{ 'nav-forward': 'slide-to-left', 'nav-back': 'slide-to-right', default: 'none' }} share={{ 'nav-forward': 'morph-forward', 'nav-back': 'morph-back', default: 'morph' }} default="none" > <Page /> </ViewTransition> ``` `enter` and `exit` don't have to be symmetric. For example, fade in but slide out directionally: ```jsx <ViewTransition enter={{ 'nav-forward': 'fade-in', 'nav-back': 'fade-in', default: 'none' }} exit={{ 'nav-forward': 'nav-forward', 'nav-back': 'nav-back', default: 'none' }} default="none" > ``` **TypeScript:** `ViewTransitionClassPerType` requires a `default` key in the object. For apps with multiple pages, extract the type-keyed VT into a reusable wrapper: ```jsx export function DirectionalTransition({ children }: { children: React.ReactNode }) { return ( <ViewTransition enter={{ 'nav-forward': 'nav-forward', 'nav-back': 'nav-back', default: 'none' }} exit={{ 'nav-forward': 'nav-forward', 'nav-back': 'nav-back', default: 'none' }} default="none" > {children} </ViewTransition> ); } ``` ### `router.back()` and Browser Back Button `router.back()` and the browser's back/forward buttons do **not** trigger view transitions (`popstate` is synchronous, incompatible with `startViewTransition`). Use `router.push()` with an explicit URL instead. ### Types and Suspense Types are available during navigation but **not** during subsequent Suspense reveals (separate transitions, no type). Use type maps for page-level enter/exit; use simple string props for Suspense reveals. --- ## Shared Element Transitions Same `name` on two VTs — one unmounting, one mounting — creates a shared element morph: ```jsx <ViewTransition name="hero-image"> <img src="/thumb.jpg" onClick={() => startTransition(() => onSelect())} /> </ViewTransition> // On the other view — same name <ViewTransition name="hero-image"> <img src="/full.jpg" /> </ViewTransition> ``` - Only one VT with a given `name` can be mounted at a time — use unique names (`photo-${id}`). Watch for reusable components: if a component with a named VT is rendered in both a modal/popover *and* a page, both mount simultaneously and break the morph. Either make the name conditional (via a prop) or move the named VT out of the shared component into the specific consumer. - `share` takes precedence over `enter`/`exit`. Think through each navigation path: when no matching pair forms (e.g., the target page doesn't have the same name), `enter`/`exit` fires instead. Consider whether the element needs a fallback animation for those paths. - Never use a fade-out exit on pages with shared morphs — use a directional slide instead. --- ## Common Patterns ### Enter/Exit ```jsx {show && ( <ViewTransition enter="fade-in" exit="fade-out"><Panel /></ViewTransition> )} ``` ### List Reorder ```jsx {items.map(item => ( <ViewTransition key={item.id}><ItemCard item={item} /></ViewTransition> ))} ``` Trigger inside `startTransition`. Avoid wrapper `<div>`s between list and VT. ### Composing Shared Elements with List Identity Shared elements and list identity are independent concerns — don't confuse one for the other. When a list item contains a shared element (e.g., an image that morphs into a detail view), use two nested `<ViewTransition>` boundaries: ```jsx {items.map(item => ( <ViewTransition key={item.id}> {/* list identity */} <Link href={`/items/${item.id}`}> <ViewTransition name={`item-image-${item.id}`} share="morph"> {/* shared element */} <Image src={item.image} /> </ViewTransition> <p>{item.name}</p> </Link> </ViewTransition> ))} ``` The outer VT handles list reorder/enter animations. The inner VT handles the cross-route shared element morph. Missing either layer means that animation silently doesn't happen. ### Force Re-Enter with `key` ```jsx <ViewTransition key={searchParams.toString()} enter="slide-up" default="none"> <ResultsGrid /> </ViewTransition> ``` **Caution:** If wrapping `<Suspense>`, changing `key` remounts the boundary and refetches. ### Suspense Fallback to Content Simple cross-fade: ```jsx <ViewTransition> <Suspense fallback={<Skeleton />}><Content /></Suspense> </ViewTransition> ``` Directional reveal: ```jsx <Suspense fallback={<ViewTransition exit="slide-down"><Skeleton /></ViewTransition>}> <ViewTransition enter="slide-up" default="none"><Content /></ViewTransition> </Suspense> ``` For more patterns, see `references/patterns.md`. --- ## How Multiple VTs Interact Every VT matching the trigger fires simultaneously in a single `document.startViewTransition`. VTs in **different** transitions (navigation vs later Suspense resolve) don't compete. ### Use `default="none"` Liberally Without it, every VT fires the browser cross-fade on **every** transition — Suspense resolves, `useDeferredValue` updates, background revalidations. Always use `default="none"` and explicitly enable only desired triggers. ### Two Patterns Coexist **Pattern A — Directional slides:** Type-keyed VT on each page, fires during navigation. **Pattern B — Suspense reveals:** Simple string props, fires when data loads (no type). They coexist because they fire at different moments. `default="none"` on both prevents cross-interference. Always pair `enter` with `exit`. Place directional VTs in page components, not layouts. ### Nested VT Limitation When a parent VT exits, nested VTs inside it do **not** fire their own enter/exit — only the outermost VT animates. Per-item staggered animations during page navigation are not possible today. See [react#36135](https://github.com/facebook/react/pull/36135) for an experimental opt-in fix. --- ## Next.js Integration For Next.js setup (`experimental.viewTransition` flag, `transitionTypes` prop on `next/link`, App Router patterns, Server Components), see `references/nextjs.md`. --- ## Accessibility Always add the reduced motion CSS from `references/css-recipes.md` to your global stylesheet. --- ## Reference Files - **`references/implementation.md`** — Step-by-step implementation workflow. - **`references/patterns.md`** — Patterns, animation timing, events API, troubleshooting. - **`references/css-recipes.md`** — Ready-to-use CSS animation recipes. - **`references/nextjs.md`** — Next.js App Router patterns and Server Component details. ## Full Compiled Document For the complete guide with all reference files expanded: `AGENTS.md` ## Limitations - Use this skill only when the task clearly matches the scope described above. - Do not treat the output as a substitute for environment-specific validation, testing, or expert review. - Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.