nextjs/no-unwanted-polyfillio Correctness

✅ This rule is turned on by default.

What it does

Prevent duplicate polyfills from Polyfill.io.

Why is this bad?

You are using polyfills from Polyfill.io and including polyfills already shipped with Next.js. This unnecessarily increases page weight which can affect loading performance.

Example

<script src='https://polyfill.io/v3/polyfill.min.js?features=Array.prototype.copyWithin'></script>

<script src='https://polyfill.io/v3/polyfill.min.js?features=WeakSet%2CPromise%2CPromise.prototype.finally%2Ces2015%2Ces5%2Ces6'></script>

How to use

To enable this rule in the CLI or using the config file, you can use:

CLI

oxlint --deny nextjs/no-unwanted-polyfillio --nextjs-plugin

Config (.oxlintrc.json)

{
  "plugins": ["nextjs"],
  "rules": {
    "nextjs/no-unwanted-polyfillio": "error"
  }
}

References

• Rule Source