Fix the Uncached Data Error in Next.js 16 — 2 Proven Fixes

I recently toggled cacheComponents: true on a side project, expecting a performance boost. Instead, I got a screen full of errors: "Uncached data was accessed outside of ". It felt like the framework was rejecting code that had worked perfectly for months. But after digging into the research, I realized this error is actually a guide. It’s Next.js 16’s way of telling you that you haven't decided what your page is yet.

In the old model, Next.js tried to guess what should be static. In the new model, you have to be explicit. If you don't choose, the compiler stops you.

What It Is

The "Uncached Data" error is an enforcement of the Static Shell + Dynamic Island architecture. When you enable Cache Components, Next.js 16 assumes that everything not wrapped in a <Suspense> boundary is part of the static shell—the part of the page that can be prerendered and served instantly from the edge.

If the compiler sees you performing async work (like a database fetch or an API call) that isn't marked with "use cache", it panics. Why? Because if that data isn't cached, the server has to wait for it. If the server has to wait, the shell isn't truly static. To fix it, you have to move that work into one of two buckets: Static (cached) or Dynamic (streamed).

Mental Model

Think of your page like a printed magazine.

• The Static Shell is the paper and the layout. It’s printed once and sent to everyone.
• The Dynamic Islands are like digital screens embedded in the paper. They update in real-time when the reader opens the magazine.

The "Uncached Data" error happens when you try to print "Live Stock Prices" directly onto the paper. The printer stops and says: "I can't print this; it changes every second. You either need to print a 'placeholder' (Suspense) and put a screen there, or decide that the price is 'Static' for this edition (use cache)."

When To Use Each Fix

When you hit this error, you have two distinct paths.

Path A: The Static Fix ('use cache') Use this if the data doesn't change per-request. If you’re fetching a list of categories or a public blog post, mark the function or component with "use cache". This tells the printer: "This data is safe to bake into the paper."

// app/components/categories.tsx
export async function Categories() {
  'use cache' // This resolves the error by making the data part of the static shell
  const categories = await db.categories.findMany()
  return <ul>{/* ... */}</ul>
}

Path B: The Dynamic Fix (<Suspense>) Use this if the data is unique to the user—like a shopping cart or a personalized greeting. By wrapping the component in <Suspense>, you are telling Next.js: "Don't wait for this. Prerender the rest of the page, send it to the user immediately, and stream this part in once it's ready."

// app/page.tsx
import { Suspense } from 'react'
import { UserProfile } from './user-profile'

export default function Page() {
  return (
    <main>
      <h1>Dashboard</h1>
      <Suspense fallback={<p>Loading profile...</p>}>
        <UserProfile /> {/* This resolves the error by moving dynamic work into a stream */}
      </Suspense>
    </main>
  )
}

Gotchas & Common Mistakes

One trap I fell into was trying to "fix" the error by adding "use cache" to everything. This is a mistake. If you cache a component that relies on cookies() or headers(), you’ll just trade your "Uncached Data" error for a "Forbidden API" error. You cannot cache per-user data without a very specific "Extraction Pattern" (passing IDs as arguments), and even then, it’s usually better to let user-specific UI be dynamic.

Another frustration is finding where the error is coming from. In a large component tree, the stack trace can be cryptic. This is where next build --debug-prerender becomes your best friend. It generates a detailed report showing exactly which component triggered a dynamic bailout, allowing you to pinpoint the missing Suspense boundary or cache directive.

Conclusion

The "Uncached Data" error isn't a hurdle; it's the framework's way of ensuring you don't accidentally ship a "slow" static page. By forcing you to choose between "use cache" and <Suspense>, Next.js 16 ensures that every route has a fast, prerendered shell. As a solo dev, embracing this error early in your build process saves you from the "why is my site slow in production?" debugging sessions later.

If you have questions or ran into a weird stack trace while debugging your shell, drop a comment below. And if you found this useful, subscribe for more.

Thanks, Matija