Private Cache

Enable runtime prefetching of personalized content by including it in prefetch requests.
Use use cache: private when you need to cache user-specific data that depends on cookies, headers, or search params.
Unlike regular use cache, private caches can access request-specific APIs like cookies() and headers() directly inside the cached function.
Private caches are never persisted to cache handlers - they're only used to mark the dynamic content as runtime prefetchable.
Without use cache: private, personalized content cannot be prefetched and must wait until navigation occurs.

app/private-cache/product/[id]/with-private/page.tsx

1async function getRecommendations(productId: string) {
2  'use cache: private';
3  cacheTag(`recommendations-${productId}`);
4  cacheLife({ stale: 60 });
5
6  // Can call cookies() INSIDE the cached function!
7  const sessionId = (await cookies()).get('session-id')?.value || 'guest';
8
9  return getPersonalizedRecommendations(productId, sessionId);
10}
11
12async function Recommendations({ productId }: { productId: string }) {
13  // This will be runtime prefetched automatically
14  const recommendations = await getRecommendations(productId);
15
16  return (
17    <div>
18      {recommendations.map((rec) => (
19        <ProductCard key={rec.id} product={rec} />
20      ))}
21    </div>
22  );
23}
24
25export const unstable_prefetch = {
26  mode: 'runtime',
27  samples: [
28    { params: { id: '1' }, cookies: [{ name: 'session-id', value: '1' }] },
29  ],
30};

Demo

Products labeled "Private Cache" link to pages that use use cache: private to enable runtime prefetching. The content is still dynamic, but it's prefetched when the static content of the page is also prefetched.
Products labeled "No Private Cache" link to pages that don't use use cache: private, meaning their recommendations will be loaded after navigation.
For demo purposes, the links display visual loading states:
- Pink border with "Prefetching Private Cache..." when the runtime prefetch is in progress
- Blue border with "Prefetched Private Cache" when the runtime prefetch has completed
- Gray border for links without private cache
With Private Cache: Personalized recommendations appear instantly (runtime prefetched).
Without Private Cache: Recommendations show a loading skeleton, then appear after they're finished loading. The loading starts when the link is clicked.
Click "Change Session" to get different personalized recommendations - notice how Private Cache links still runtime prefetch your new session's data.

Notes

use cache: private enables runtime prefetching of personalized content by allowing request-specific APIs inside cached functions.
Combine with unstable_prefetch export using mode: 'runtime' and appropriate cacheLife settings.

Visual Summary

Private cache prefetch

Prefetch

use cache: private

Runtime

Personalized UI

Private cache enables runtime prefetching for user-specific data.

Key Takeaways

Topic	Guidance
Use case	Personalized data that still benefits from prefetch
Scope	Private caches never persist to shared cache handlers
UX	Makes dynamic content feel instant