Next.js 15 Caching Explained: Why Your Data Keeps Showing as Stale

If you upgraded from Next.js 14 to 15 and your pages suddenly stopped refreshing — or started hitting your database on every request — you are not alone. The caching model changed fundamentally. This is the guide I wish existed when I spent a day debugging it.

What Changed in Next.js 15

In Next.js 14, fetch() inside Server Components was cached by default:

// Next.js 14: this was CACHED (force-cache) const data = await fetch ( ' https://api.example.com/posts ' );

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In Next.js 15, the default flipped:

// Next.js 15: this is NOT cached (no-store) const data = await fetch ( ' https://api.example.com/posts ' );

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This single change affects every Server Component in your app that uses fetch() .…