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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

The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.

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

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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.

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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.

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HTML 

              
                <article class="flow">
  <h1>Nulla vitae elit libero, a pharetra augue</h1>
  <p class="lede">Nulla vitae elit libero, a pharetra augue. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Maecenas faucibus mollis interdum. Donec sed odio dui.</p>
  <p>Nullam quis risus eget urna mollis ornare vel eu leo. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Fusce dapibus, tellus ac cursus commodo, tortor mauris condimentum nibh, ut fermentum massa justo sit amet risus. Aenean lacinia bibendum nulla sed consectetur.</p>
  <h2>Donec id elit non mi porta gravida at eget metus</h2>
  <p>Aenean eu leo quam. <a href="http://example.com">Pellentesque ornare sem</a> lacinia quam venenatis vestibulum. Morbi leo risus, porta ac consectetur ac, vestibulum at eros. Integer posuere erat a ante venenatis dapibus posuere velit aliquet. Nulla vitae elit libero, a pharetra augue. Maecenas sed diam eget risus varius blandit sit amet non magna.</p>
  <p>Maecenas sed diam eget risus varius blandit sit amet non magna. Cras mattis consectetur purus sit amet fermentum. Nulla vitae elit libero, a pharetra augue. Donec sed odio dui. Aenean lacinia bibendum nulla sed consectetur. Curabitur blandit tempus porttitor.</p>
  <blockquote>
    <q>Cras justo odio, dapibus ac facilisis in, egestas eget quam. <strong>Sed posuere</strong> consectetur est at lobortis. Integer posuere erat a ante venenatis dapibus posuere velit aliquet.</q>
  </blockquote>
  <h3>Sed posuere consectetur est at lobortis</h3>
  <p>Fusce dapibus, <em>tellus ac cursus commodo</em>, tortor mauris condimentum nibh, ut fermentum massa justo sit amet risus. Morbi leo risus, porta ac consectetur ac, vestibulum at eros. Etiam porta sem malesuada magna mollis euismod. Nulla vitae elit libero, a pharetra augue.</p>
  <h2>Ut fermentum massa justo sit amet risus</h2>
  <ul>
    <li>Lorem ipsum dolor sit amet, consectetuer adipiscing elit</li>
    <li>Aliquam tincidunt mauris eu risus</li>
    <li>Vestibulum auctor dapibus neque</li>
  </ul>
  <p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo. Quisque sit amet est et sapien ullamcorper pharetra. Vestibulum erat wisi, condimentum sed, commodo vitae, ornare sit amet, wisi. Aenean fermentum, elit eget tincidunt condimentum, eros ipsum rutrum orci, sagittis tempus lacus enim ac dui. Donec non enim in turpis pulvinar facilisis. Ut felis. Praesent dapibus, neque id cursus faucibus, tortor neque egestas augue, eu vulputate magna eros eu erat. Aliquam erat volutpat. Nam dui mi, tincidunt quis, accumsan porttitor, facilisis luctus, metus</p>
</article>
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CSS 

              
                /* @link https://utopia.fyi/type/calculator?c=320,18,1.25,1240,18,1.333,5,2,&s=0.75|0.5|0.25,1.5|2|3|4|6,s-l&g=s,l,xl,12 */

:root {
  --color-dark: #000000;
  --color-light: #ffffff;
  --color-primary: #1a8fe3;
  --size-step-0: clamp(1rem, calc(0.96rem + 0.22vw), 1.13rem);
  --size-step-1: clamp(1.25rem, calc(1.16rem + 0.43vw), 1.5rem);
  --size-step-2: clamp(1.56rem, calc(1.41rem + 0.76vw), 2rem);
  --size-step-3: clamp(1.95rem, calc(1.71rem + 1.24vw), 2.66rem);
  --size-step-4: clamp(2.44rem, calc(2.05rem + 1.93vw), 3.55rem);
}

body {
  background: var(--color-light);
  color: var(--color-dark);
  padding: 2em;
  font-family: Georgia, serif;
  font-size: var(--size-step-0);
  line-height: 1.7;
}

h1,
h2,
h3 {
  font-family: Inter, sans-serif;
  font-weight: 800;
  line-height: 1.1;
}

h1 {
  font-size: var(--size-step-4);
}

h2 {
  font-size: var(--size-step-3);
}

h3 {
  font-size: var(--size-step-2);
}

ul,
ol {
  padding-inline-start: 1em;
}

blockquote {
  padding-inline-start: 1em;
  border-inline-start: 0.3em solid;
  font-style: italic;
  font-size: var(--size-step-1);
}

/* Utilities */
.flow > * + * {
  margin-block-start: var(--flow-space, 1em);
}

/* Flow and rythm */
:is(h1, h2, h3, blockquote) {
  --flow-space: 1.5em;
}

:is(h1, h2, h3) + * {
  --flow-space: 0.5em;
}
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JS
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999px

Console