During a build, Next.js will automatically trace each page and its dependencies to determine all of the files that are needed for deploying a production version of your application.
This feature helps reduce the size of deployments drastically. Previously, when deploying with Docker you would need to have all files from your package's dependencies
installed to run next start
. Starting with Next.js 12, you can leverage Output File Tracing in the .next/
directory to only include the necessary files.
Furthermore, this removes the need for the deprecated serverless
target which can cause various issues and also creates unnecessary duplication.
During next build
, Next.js will use @vercel/nft
to statically analyze import
, require
, and fs
usage to determine all files that a page might load.
Next.js' production server is also traced for its needed files and output at .next/next-server.js.nft.json
which can be leveraged in production.
To leverage the .nft.json
files emitted to the .next
output directory, you can read the list of files in each trace which are relative to the .nft.json
file and then copy them to your deployment location.
Next.js can automatically create a standalone
folder which copies only the necessary files for a production deployment including select files in node_modules
.
To leverage this automatic copying you can enable it in your next.config.js
:
module.exports = {
experimental: {
outputStandalone: true,
},
}
This will create a folder at .next/standalone
which can then be deployed on it's own without installing node_modules
.
Additionally, a minimal server.js
file is also output which can be used instead of next start
. This minimal server does not copy the .next/static
directory by default as this should ideally be handled by a CDN instead, although it can be copied to the standalone
folder manually and the server.js
file will serve it automatically.
next build packages/web-app
, packages/web-app
would be the tracing root and any files outside of that folder will not be included. To include files outside of this folder you can set experimental.outputFileTracingRoot
in your next.config.js
.// packages/web-app/next.config.js
module.exports = {
experimental: {
// this includes files from the monorepo base two directories up
outputFileTracingRoot: path.join(__dirname, '../../'),
},
}
unstable_includeFiles
and unstable_excludeFiles
respectively. Each prop accepts an array of globs relative to the project's root to either include or exclude in the trace..nft.json
files. The files must be read by your deployment platform, for example Vercel, to create a minimal deployment. In a future release, a new command is planned to utilize these .nft.json
files.