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

yarn policies

Defines project-wide policies for your project.

Enforcing Yarn’s version across your project

When working inside a team, you usually end up in the situation where one of your colleagues uses a different version of Yarn than you. While usually inconsequential, it might sometimes cause subtle and hard to debug issues - for example your colleague might be on a version of Yarn that doesn’t support a feature you rely on, such as the workspaces.

In order to alleviate this issue, you can specify the required Yarn version inside the package.json file, which will prompt your colleagues to use the same version as you. Unfortunately, while technically strong, this technique adds an unwanted burden on them - given that the Yarn binary is typically global, switching from a branch to another might be particularly annoying if they change the version.

To fix that, yarn policies set-version offers a simple way to check in your Yarn release within your repository. Once you run it, your configuration will be updated in such a way that anyone running a Yarn command inside the project will always use the version you set - and this transparently.

The command accepts various ways to set which version you want to use:

  • yarn policies set-version will download the latest stable release
  • yarn policies set-version --rc will download the latest rc release
  • yarn policies set-version 1.13.0 will download a specific version
  • yarn policies set-version '^1.12.0' will download the latest minor

Under the hood, the command will simply download the single-file release from the GitHub repository, store it inside your project (inside the .yarn/releases folder), then finally update your configuration to point to the new file (using yarn-path).

Note that this command also is the preferred way to upgrade Yarn - it will work no matter how you originally installed it, which might sometimes prove difficult to figure out otherwise.