CDN Support with Asset Prefix

Attention: Deploying to Vercel automatically configures a global CDN for your Next.js project. You do not need to manually setup an Asset Prefix.

Note: Next.js 9.5+ added support for a customizable Base Path, which is better suited for hosting your application on a sub-path like /docs. We do not suggest you use a custom Asset Prefix for this use case.

To set up a CDN, you can set up an asset prefix and configure your CDN's origin to resolve to the domain that Next.js is hosted on.

Open next.config.js and add the assetPrefix config:

const isProd = process.env.NODE_ENV === 'production'

module.exports = {
  // Use the CDN in production and localhost for development.
  assetPrefix: isProd ? 'https://cdn.mydomain.com' : undefined,
}

Next.js will automatically use your asset prefix for the JavaScript and CSS files it loads from the /_next/ path (.next/static/ folder). For example, with the above configuration, the following request for a JS chunk:

/_next/static/chunks/4b9b41aaa062cbbfeff4add70f256968c51ece5d.4d708494b3aed70c04f0.js

Would instead become:

https://cdn.mydomain.com/_next/static/chunks/4b9b41aaa062cbbfeff4add70f256968c51ece5d.4d708494b3aed70c04f0.js

The exact configuration for uploading your files to a given CDN will depend on your CDN of choice. The only folder you need to host on your CDN is the contents of .next/static/, which should be uploaded as _next/static/ as the above URL request indicates. Do not upload the rest of your .next/ folder, as you should not expose your server code and other configuration to the public.

While assetPrefix covers requests to _next/static, it does not influence the following paths:

  • Files in the public folder; if you want to serve those assets over a CDN, you'll have to introduce the prefix yourself
  • /_next/data/ requests for getServerSideProps pages. These requests will always be made against the main domain since they're not static.
  • /_next/data/ requests for getStaticProps pages. These requests will always be made against the main domain to support Incremental Static Generation, even if you're not using it (for consistency).

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