; } } ``` **This is not required for React** but many people find this feature convenient. You can read about the benefits of this approach [here](https://medium.com/seek-ui-engineering/block-element-modifying-your-javascript-components-d7f99fcab52b). However you should be aware that this makes your code less portable to other build tools and environments than Webpack. In development, expressing dependencies this way allows your styles to be reloaded on the fly as you edit them. In production, all CSS files will be concatenated into a single minified `.css` file in the build output. If you are concerned about using Webpack-specific semantics, you can put all your CSS right into `src/index.css`. It would still be imported from `src/index.js`, but you could always remove that import if you later migrate to a different build tool. ## Post-Processing CSS This project setup minifies your CSS and adds vendor prefixes to it automatically through [Autoprefixer](https://github.com/postcss/autoprefixer) so you don’t need to worry about it. For example, this: ```css .App { display: flex; flex-direction: row; align-items: center; } ``` becomes this: ```css .App { display: -webkit-box; display: -ms-flexbox; display: flex; -webkit-box-orient: horizontal; -webkit-box-direction: normal; -ms-flex-direction: row; flex-direction: row; -webkit-box-align: center; -ms-flex-align: center; align-items: center; } ``` There is currently no support for preprocessors such as Less, or for sharing variables across CSS files. ## Adding Images and Fonts With Webpack, using static assets like images and fonts works similarly to CSS. You can **`import` an image right in a JavaScript module**. This tells Webpack to include that image in the bundle. Unlike CSS imports, importing an image or a font gives you a string value. This value is the final image path you can reference in your code. Here is an example: ```js import React from 'react'; import logo from './logo.png'; // Tell Webpack this JS file uses this image console.log(logo); // /logo.84287d09.png function Header() { // Import result is the URL of your image return

; } export default Header; ``` This ensures that when the project is built, Webpack will correctly move the images into the build folder, and provide us with correct paths. This works in CSS too: ```css .Logo { background-image: url(./logo.png); } ``` Webpack finds all relative module references in CSS (they start with `./`) and replaces them with the final paths from the compiled bundle. If you make a typo or accidentally delete an important file, you will see a compilation error, just like when you import a non-existent JavaScript module. The final filenames in the compiled bundle are generated by Webpack from content hashes. If the file content changes in the future, Webpack will give it a different name in production so you don’t need to worry about long-term caching of assets. Please be advised that this is also a custom feature of Webpack. **It is not required for React** but many people enjoy it (and React Native uses a similar mechanism for images).
An alternative way of handling static assets is described in the next section. ## Using the `public` Folder >Note: this feature is available with `react-scripts@0.5.0` and higher. Normally we encourage you to `import` assets in JavaScript files as described above. This mechanism provides a number of benefits: * Scripts and stylesheets get minified and bundled together to avoid extra network requests. * Missing files cause compilation errors instead of 404 errors for your users. * Result filenames include content hashes so you don’t need to worry about browsers caching their old versions. However there is an **escape hatch** that you can use to add an asset outside of the module system. If you put a file into the `public` folder, it will **not** be processed by Webpack. Instead it will be copied into the build folder untouched. To reference assets in the `public` folder, you need to use a special variable called `PUBLIC_URL`. Inside `index.html`, you can use it like this: ```html ``` Only files inside the `public` folder will be accessible by `%PUBLIC_URL%` prefix. If you need to use a file from `src` or `node_modules`, you’ll have to copy it there to explicitly specify your intention to make this file a part of the build. When you run `npm run build`, Create React App will substitute `%PUBLIC_URL%` with a correct absolute path so your project works even if you use client-side routing or host it at a non-root URL. In JavaScript code, you can use `process.env.PUBLIC_URL` for similar purposes: ```js render() { // Note: this is an escape hatch and should be used sparingly! // Normally we recommend using `import` for getting asset URLs // as described in “Adding Images and Fonts” above this section. return

; } ``` Keep in mind the downsides of this approach: * None of the files in `public` folder get post-processed or minified. * Missing files will not be called at compilation time, and will cause 404 errors for your users. * Result filenames won’t include content hashes so you’ll need to add query arguments or rename them every time they change. However, it can be handy for referencing assets like [`manifest.webmanifest`](https://developer.mozilla.org/en-US/docs/Web/Manifest) from HTML, or including small scripts like [`pace.js`](http://github.hubspot.com/pace/docs/welcome/) outside of the bundled code. Note that if you add a `