---
title: Dedupe
description: Prevent duplicate work by deduplicating function calls.
---

# Dedupe



Any function wrapped in `dedupe` will only ever run once for
the same request within the same runtime and given the same arguments.

The `dedupe` function is an integral piece when working with
the Flags SDK.

## Example

```tsx title="app/page.tsx"
import { dedupe } from 'flags/next';

const dedupeExample = dedupe(() => {
  return Math.random();
});

export default async function Page() {
  const random1 = await dedupeExample();
  const random2 = await dedupeExample();
  const random3 = await dedupeExample();

  // these will all be the same random number
  return (
    <div>
      {random1} {random2} {random3}
    </div>
  );
}
```

Example of output:

<IframeBrowser src="snippets:/concepts/dedupe" codeSrc="https://github.com/vercel/flags/blob/main/examples/snippets/app/concepts/dedupe/page.tsx" />

## Use cases

### Avoiding duplicate work

This helper is useful in combination with the `identify` function, as it
allows the identification to only happen once per request.
This prevents overhead when passing the same{" "}
`identify` function to multiple feature flags, or when using the same flag multiple times.

### Generating consistent random IDs

When experimenting on anonymous visitors it is common to set a cookie
containing a random id from Proxy. This random id is later
used to consistently assign users to specific groups of A/B tests.

For this use case, the function generating the random id can be wrapped
in `dedupe`. The deduplicated function is then called in Routing
Functions to produce the random id, and from a flag's{" "}
`identify` function to identify the user even on the first
page visit when no cookie is present yet.

As the function is guaranteed to generate the same id the Routing
Functions can set a cookie containing the generated id in a response,
and the feature flag can already use the generated id even if the
original request did not contain the id.

## Limitations

Note that `dedupe` is not available in Pages Router.

<LearnMore href="/frameworks/next/guides/marketing-pages" icon="arrow">
  See the Marketing Pages example
</LearnMore>