Important: This documentation covers Yarn 1 (Classic).
For Yarn 2+ docs and migration guide, see

yarn import

Generates yarn.lock from an npm package-lock.json file in the same location or an existing npm-installed node_modules folder.

yarn import

This command assists the migration of projects currently relying on package-lock.json, minimizing the differences between the lockfile and the existing dependency tree as best as it can.


Many projects currently use package-lock.json or check their node_modules into source control because they have fragile dependency trees. These projects can’t easily migrate to Yarn, because yarn install could produce a wildly different logical dependency tree. Not all trees can be represented by Yarn’s yarn.lock, and some valid trees will be automatically deduped upon install. These nuances and others present a significant barrier to manual migration.

yarn import aims to alleviate this challenge by generating a yarn.lock file in one of two ways:

  1. Using the dependency tree in an existing package-lock.json file created by npm install
  2. If no such file exists, using the versions found inside node_modules according to normal require.resolve() resolution rules.

In cases where the Yarn resolution mechanism can’t satisfy the existing dependency tree identically, alerts will be made so that you may manually review the changes. The existing node_modules tree will be checked for validity beforehand (if not importing from package-lock.json), and the resultant lockfile should be yarn installable without any surprises (failed compatibility, unresolvable dependencies, auto-dedupes, etc.)

$ yarn import
yarn import vx.x.x
success Folder in sync.
warning Using version "2.2.4" of "lru-cache" instead of "2.7.3" for "ngstorage > grunt > minimatch"
warning Using version "2.0.6" of "readable-stream" instead of "2.2.9" for "ngstorage > karma > chokidar > readdirp"
success Saved lockfile.
✨  Done in 11.96s.