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HTML

About HTML Preprocessors

HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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Adding Classes

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. So you don't have access to higher-up elements like the <html> tag. If you want to add classes there that can affect the whole document, this is the place to do it.

About the <head>

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. If you need things in the <head> of the document, put that code here.

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Insecure Resource

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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

Add External Stylesheets/Pens

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You can apply CSS to your Pen from any stylesheet on the web. Just put a URL to it here and we'll apply it, in the order you have them, before the CSS in the Pen itself.

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

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You can apply a script from anywhere on the web to your Pen. Just put a URL to it here and we'll add it, in the order you have them, before the JavaScript in the Pen itself.

If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.

You can also link to another Pen here, and we'll pull the JavaScript from that Pen and include it. If it's using a matching preprocessor, we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.

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Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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About Packages

Using packages here is powered by esm.sh, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ESM usage.

All packages are different, so refer to their docs for how they work.

If you're using React / ReactDOM, make sure to turn on Babel for the JSX processing.

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HTML 

              
                
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Praesent bibendum, lorem vel tincidunt imperdiet, nibh elit laoreet felis, a bibendum nisl tortor non orci. Donec pretium fermentum felis, <a href="#">quis aliquet est rutrum ut. Integer quis massa ut lacus viverra pharetra in eu lacus. Aliquam tempus odio adipiscing diam pellentesque rhoncus.</a> Curabitur a bibendum est. Mauris vehicula cursus risus id luctus. Curabitur accumsan venenatis nibh, non egestas ipsum vulputate ac. Vivamus consectetur dolor sit amet enim aliquet eu scelerisque ipsum hendrerit. Donec lobortis suscipit vestibulum. Nullam luctus pellentesque risus in ullamcorper. Nam neque nunc, mattis vitae ornare ut, feugiat a erat. Ut tempus iaculis augue vel pellentesque.</p>

<p>Vestibulum nunc massa, gravida quis porta nec, feugiat id metus. <a href="#" class="strike">Strike me! Nunc ac arcu dolor, quis vestibulum leo. Cras viverra mollis ipsum, non rhoncus lectus aliquam et.</a> Morbi faucibus purus sit amet lacus aliquet elementum. Donec sit amet posuere enim. Cras in eros id tortor fringilla ultricies. Mauris faucibus ullamcorper velit, pulvinar varius odio eleifend eu. Quisque id odio metus. Morbi adipiscing ultricies posuere. Pellentesque elementum porttitor eros in molestie. Maecenas ut leo quis nisi tempor tincidunt.</p>

<p>Donec nunc ligula, vulputate quis mollis eu, interdum quis libero. Donec nulla ante, facilisis sit amet vulputate at, tincidunt a velit. Maecenas vestibulum, nulla sed tincidunt viverra, lorem turpis aliquam urna, ut pretium orci purus consequat augue. Etiam a enim orci, vitae pulvinar odio. In elit urna, tincidunt a pellentesque et, scelerisque at nibh. <a href="#">Sed nec est sapien. Aliquam ullamcorper eros eu quam ultrices vel faucibus eros interdum. Etiam mattis eleifend sapien, eu iaculis massa feugiat sed. Aliquam erat volutpat.</a> Vivamus facilisis ultricies eros, a pretium purus mollis id. Sed dapibus elit ut neque rutrum dignissim. Nulla eros nisl, venenatis quis rhoncus sit amet, molestie nec nisl. Pellentesque vel neque sapien, et sagittis nulla.</p>

<p>Aliquam eu iaculis mauris. Etiam arcu lectus, imperdiet sit amet volutpat vitae, commodo sed nibh. Fusce faucibus tempor cursus. Donec ut ligula tortor. <a href="#">Maecenas malesuada, diam vitae pharetra dictum, erat ante iaculis risus, sed sollicitudin nisl nisl vel metus.</a> Nulla libero augue, convallis nec luctus id, iaculis nec urna. Cras vitae mi ut augue ultricies tempus.</p>
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CSS 

              
                a, .strike { 
  color: #FF5151;
  text-decoration: none;
  display: inline;
  background-image: linear-gradient(to bottom, transparent 20%, currentColor 21%);
  
  background-position: 0 1em;
  background-repeat: no-repeat;
  background-size: 0% 6px;
  
  transition: background-size 0.5s ease-in-out 0.2s;
}

a:hover,
a:focus {
  background-size: 100% 6px;
  transition-delay: 0s;
}

.strike {
  color: #307672;
  background-size: 0% 2px;
  background-position: 0 0.5em; /*1em;*/
}

.strike:hover,
.strike:focus {
  background-size: 100% 2px;
  transition-delay: 0s;
}

html { 
  background: #000249; 
  color: #FFF;
  font-size: 62.5%;
  display: flex;
  height: 100%;
}

body { 
  font-size: 1.6rem;
  line-height: 1.4;
  max-width: 30em;
  width: 90%;
  margin: auto;
  background: inherit;
  -webkit-font-smoothing: antialiased;
  font-smoothing: always;
}
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JS
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999px

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