# only-allow > Force a specific package manager to be used on a project ## Usage Add a `preinstall` script to your project's `package.json`. If you want to force [npm](https://docs.npmjs.com/cli/npm), add: ```json { "scripts": { "preinstall": "npx only-allow npm" } } ``` If you want to force [cnpm](https://npmmirror.com/), add: ```json { "scripts": { "preinstall": "npx only-allow cnpm" } } ``` If you want to force [pnpm](https://pnpm.js.org/), add: ```json { "scripts": { "preinstall": "npx only-allow pnpm" } } ``` If you want to force [yarn](https://yarnpkg.com/), add: ```json { "scripts": { "preinstall": "npx only-allow yarn" } } ``` ## License [MIT](LICENSE)