I&#39;m working on a web project using Babel 7 with Webpack 4. I&#39;ve never used Babel before and can&#39;t really understand some parts of it. Based on the [documentation][1] I&#39;m using `@babel/preset-env` because it seems the recommended way (especially for beginners). Also using Browserslist integration via my `.browserslistrc` file.

Webpack does the compilation well (`babel-loader` version `8.0.2`), I have no errors but I&#39;m confused about this `useBuiltIns: &quot;entry&quot;` [option mentioned here][2] and how `polyfill` system is working in Babel.  

**.babelrc.js**

    module.exports = {
      presets: [
        [&#39;@babel/preset-env&#39;, {
          &quot;useBuiltIns&quot;: &quot;entry&quot; // do I need this?
        }]
      ],
      plugins: [
        &#39;@babel/plugin-syntax-dynamic-import&#39;
      ]
    };

**.browserslistrc**  
Copied from [here][3] (thought reasonable because my project is using Bootstrap).

    &gt;= 1%
    last 1 major version
    not dead
    Chrome &gt;= 45
    Firefox &gt;= 38
    Edge &gt;= 12
    Explorer &gt;= 10
    iOS &gt;= 9
    Safari &gt;= 9
    Android &gt;= 4.4
    Opera &gt;= 30

**So my questions are:**

1) Do I need to use that `useBuiltIns: &quot;entry&quot;` option?

2) Do I need to install `@babel/polyfill` package and start my `vendors.js` with `require(&quot;@babel/polyfill&quot;);` ?  

3) What if I omit both?

If I do 1 and 2, my `vendors.js` grows up to `411 KB`  
If I ommit both it&#39;s just `341 KB`  
after a production build.

I thought `@babel/preset-env` handles all the rewrites and polyfills by default without any extra `import/require` needed on my side...

Thanks!

**-- EDIT --**

*Babel&#39;s team has just [updated][4] the [docs of `@babel/polyfill`][5] based on some GitHub issues (including mine) complaining about unclear/misleading documentation. Now it&#39;s obvious how to use it. (...and after that my original question seems stupid :)*


  [1]: https://babeljs.io/docs/en/babel-preset-env
  [2]: https://babeljs.io/docs/en/babel-preset-env#browserslist-integration
  [3]: https://github.com/twbs/bootstrap/blob/v4.1.3/.browserslistrc
  [4]: https://github.com/babel/website/pull/1858
  [5]: https://babeljs.io/docs/en/babel-polyfill#usage-in-node-browserify-webpack

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Confused about useBuiltIns option of @babel/preset-env (using Browserslist Integration)