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


Environment variables defined in process.env allow you to configure additional Yarn features.



Controls the number of child processes run in parallel to build node modules.

Setting this number to 1 will cause the node modules to be built sequentially which can avoid linker errors on windows with node-gyp.


For backward compatibility with npm, Yarn allows passing down npm configuration via environment variables. For instance, the --build-from-source npm CLI flag becomes: npm_config_build_from_source=true. For more information on configuring npm, refer to the npm-config page.