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DocsErrorsCannot infer intended usage of `Math.random()` in a Server Component

Cannot infer intended usage of `Math.random()` in a Server Component

Why This Error Occurred

A Server Component is calling Math.random() without specifying whether it should be cached or whether it should be evaluated on each user Request. If you want this random value to be included in the prerendered HTML for this page you must cache it using "use cache". If you want this random value to be unique per Request you must precede it with await connection() so Next.js knows to exclude it from the prerendered HTML.

Possible Ways to Fix It

Cache the random value

If your random value is cacheable, move the Math.random() call to a "use cache" function. For instance, imagine you have a product page and you want to randomize the product order periodically but you are fine with the random order being re-used for different users.

Before:

app/page.js
export default async function Page() {
  const products = await getCachedProducts()
  const randomSeed = Math.random()
  const randomizedProducts = randomize(products, randomSeed)
  return <ProductsView products={randomizedProducts} />
}

After:

app/page.js
export default async function Page() {
  'use cache'
  const products = await getCachedProducts()
  const randomSeed = Math.random()
  const randomizedProducts = randomize(products, randomSeed)
  return <ProductsView products={randomizedProducts} />
}

Note: "use cache" is a powerful API with some nuances. If your cache lifetime is too short Next.js may still exclude it from prerendering. Check out the docs for "use cache" to learn more.

Indicate the random value is unique per Request

If you want the random value to be evaluated on each Request precede it with await connection(). Next.js will exclude this Server Component from the prerendered HTML and include the fallback UI from the nearest Suspense boundary wrapping this component instead. When a user makes a Request for this page the Server Component will be rendered and the updated UI will stream in dynamically.

Before:

app/page.js
export default async function Page() {
  const products = await getCachedProducts()
  const randomSeed = Math.random()
  const randomizedProducts = randomize(products, randomSeed)
  return <ProductsView products={randomizedProducts} />
}

After:

app/page.js
import { connection } from 'next/server'
 
async function ProductsSkeleton() {
  ...
}
 
export default async function Page() {
  const products = await getCachedProducts();
  return (
    <Suspense fallback={<ProductsSkeleton />}>
      <DynamicProductsView products={products} />
    </Suspense>
  )
}
 
async function DynamicProductsView({ products }) {
  await connection();
  const randomSeed = Math.random()
  const randomizedProducts = randomize(products, randomSeed)
  return <ProductsView products={randomizedProducts} />
}