Angular - including CSS file in index.html

Basically there are three different ways to do that :-

1. By adding it to the "styles" array in angular-cli.json file as is shown by @penleychan in his answer.

"styles": [
        "../node_modules/bootstrap/dist/css/bootstrap.min.css",
        "styles.css"
      ]

2. You can directly import the css file into styles.css file (or any other css file) that is included in "styles" array in angular-cli.json file by adding the @import statement at the top of that file.

@import "~bootstrap/dist/css/bootstrap.min.css";

3. Include the css file in index.html page by adding a link element.

<link rel="stylesheet" type="text/css" href="node_modules/bootstrap/dist/css/bootstrap.min.css" />

You can find a more elaborated explanation and a few more alternatives at this link

How to Use Angular with Linked Cascading Style Sheets (CSS)

Always use LINKED CSSS rather than the compiled and embedded JavaScript memory version of CSS Google Angular uses. Why? Linked <link> external CSS is superior in every way to embedded CSS, mainly because linked CSS is cached across thousands of page views, visits, and users online, saving you huge bandwidth values with increased CSS rendering speed in the browser, while implementing simpler, faster CSS management, overall.

HOW TO FIX ANGULAR FOR LINKED CSS

1. In angular.json delete all the references to CSS files under "styles". It should look like this now:

     "styles": [],
   

2. Move your CSS files to the"src" folder inside your project, then add links <link> to your external CSS files inside index.html. Add in your link paths to your CSS file starting at the "src" folder and including the "styles" folder or any folder system you desire (see below). You can store your css wherever you want in your project now as long as those folders of files are under your "src" root folder. My physical CSS files in my project for the path below now sit under "src/styles". So the link path should just be my "styles" folder plus the file name:

    <link href="styles/mystyles.css" rel="stylesheet" />

3. Any CSS files for bootstrap, font-awesome, etc. that you want in your project have to be manually copied from your "node_modules" folder in your project into a folder under your "src" folder, just like in the location used for the CSS file above in #2. Or, you can reference them from some fully qualified url online. If you want to create a link to them as above in "index.html", or import them into the html file directly (example below), that will also work. If you were importing them before from the "node_modules" folder that will not work as the Angular CLI or webpack resolved those paths by compiling your CSS imports into JavaScript. After you move those CSS files and link or import them from the src folder, they will not be compiled into Angular JavaScript now. When using @import, be sure to drop your bootstrap and font-awesome CSS files in the same "src/styles" folder as your main style sheet and import them into that stylesheet like this:

    <style type="text/css">
        @import "bootstrap.min.css";
        @import "font-awesome.min.css";
    </style>

4. In the same angular.json file above, under the "assets" JSON setting, add a reference to the location of your CSS files in #2 and #3 so the builder can copy them into your dist folder. Any CSS files linked or imported from that folder will get moved by the "dist" folder system when Angular is compiled. Note the new styles path at the bottom. If you have CSS in other folders you can add them here as well. This tells the builder to create the CSS directories in the "dist" folder Angular uses and copy all the CSS files inside them, so when you build for production your index.html links point to the right CSS files on the server:

    "assets": [
      "src/favicon.ico",
      "src/assets",
      "src/api",
      "src/styles"
    ],
   

You now have a powerful set of link elements to all your CSS in the head of your index.html file and can edit them in the Angular project like you normally do, knowing they will work in both the Angular development test server and in your dist production copy. Your website will also benefit from browser caching of CSS one time in memory and permanent file caches.

It took me a day to dig through documentation and testing to figure out what should have been a natural part of any simple website API with linked CSS. I'm sorry Google Angular made this so convoluted. But this change works great!

This simply removes your CSS from the compile and build angular system that pushes all your CSS into a JavaScript file, which simply embedded your CSS into an inline style sheet block in the memory of your browser and head of your HTML page. Using your own linked CSS html tags is far superior and allows better caching and control of CSS cascade rules.

Good Luck!