Client Swr Dedup

---
description: Imported skill client_swr_dedup from vercel
name: client_swr_dedup
signature: 644652c39c6cc00de8d1c77a7273612e868dc3f7edda30764164c12ec0f764a3
source: /a0/tmp/skills_research/vercel/skills/react-best-practices/rules/client-swr-dedup.md
---

---
title: Use SWR for Automatic Deduplication
impact: MEDIUM-HIGH
impactDescription: automatic deduplication
tags: client, swr, deduplication, data-fetching
---

## Use SWR for Automatic Deduplication

SWR enables request deduplication, caching, and revalidation across component instances.

**Incorrect (no deduplication, each instance fetches):**

```tsx
function UserList() {
  const [users, setUsers] = useState([])
  useEffect(() => {
    fetch('/api/users')
      .then(r => r.json())
      .then(setUsers)
  }, [])
}
```

**Correct (multiple instances share one request):**

```tsx
import useSWR from 'swr'

function UserList() {
  const { data: users } = useSWR('/api/users', fetcher)
}
```

**For immutable data:**

```tsx
import { useImmutableSWR } from '@/lib/swr'

function StaticContent() {
  const { data } = useImmutableSWR('/api/config', fetcher)
}
```

**For mutations:**

```tsx
import { useSWRMutation } from 'swr/mutation'

function UpdateButton() {
  const { trigger } = useSWRMutation('/api/user', updateUser)
  return <button onClick={() => trigger()}>Update</button>
}
```

Reference: [https://swr.vercel.app](https://swr.vercel.app)