# babel-plugin-transform-strict-mode > This plugin places a `"use strict";` directive at the top of all files to enable [strict mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode). This plugin may be enabled via `babel-plugin-transform-es2015-modules-commonjs`. If you wish to disable it you can either turn `strict` off or pass `strictMode: false` as an option to the commonjs transform. ## Example **In** ```javascript foo(); ``` **Out** ```javascript "use strict"; foo(); ``` ## Installation ```sh npm install --save-dev babel-plugin-transform-strict-mode ``` ## Usage ### Via `.babelrc` (Recommended) **.babelrc** Without options: ```json { "plugins": ["transform-strict-mode"] } ``` With options: ```json { "plugins": [ ["transform-strict-mode", { "strict": true }] ] } ``` ### Via CLI ```sh babel --plugins transform-strict-mode script.js ``` ### Via Node API ```javascript require("babel-core").transform("code", { plugins: ["transform-strict-mode"] }); ```