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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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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

Any URLs added here will be added as <link>s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.

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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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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.

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HTML 

              
                - 
  spaces = [
    {
      name: 'hex',
      examples: [
        '#4095bf',
        '#49b',
        '#4095bfff',
        '#49bf',
        '#4095bf80',
        '#49b8',
        '#ffffff',
        '#fff',
        '#ffffffff',
        '#ffff',
        '#000000',
        '#000',
        '#000000ff',
        '#000f', 
      ]
    },
    {
      name: 'rgb',
      examples: [
        'rgb(64, 149, 191)',
        'rgb(64 149 191)',
        'rgb(25% 58% 75%)',
        'rgba(64, 149, 191, 50%)',
        'rgba(64, 149, 191, .5)',
        'rgb(64 149 191 / 50%)',
        'rgb(64 149 191 / .5)',
        'rgb(25% 58% 75% / 50%)',
        'rgb(25% 58% 75% / .5)',
        'rgb(255, 255, 255)',
        'rgb(255 255 255)',
        'rgb(100% 100% 100%)',
        'rgb(0, 0, 0)',
        'rgb(0 0 0)',
        'rgb(0% 0% 0%)',
        'rgb(none none none)',
      ]
    },
    {
      name: 'srgb',
      examples: [
        'color(srgb 34% 58% 73%)',
        'color(srgb .34 .58 .73)',
        'color(srgb 34% 58% 73% / 50%)',
        'color(srgb .34 .58 .73 / .5)',
        'color(srgb 100% 100% 100%)', 
        'color(srgb 1 1 1)', 
        'color(srgb 0% 0% 0%)', 
        'color(srgb 0 0 0)', 
        'color(srgb none none none)', 
        'color(srgb 0)',
        'color(srgb)',
      ]
    },
    {
      name: 'srgb-linear',
      examples: [
        'color(srgb-linear 5% 30% 52%)',
        'color(srgb-linear .05 .3 .52)',
        'color(srgb-linear 5% 30% 52% / 50%)',
        'color(srgb-linear .05 .3 .52 / .5)',
        'color(srgb-linear 100% 100% 100%)', 
        'color(srgb-linear 1 1 1)', 
        'color(srgb-linear 0% 0% 0%)', 
        'color(srgb-linear 0 0 0)', 
        'color(srgb-linear none none none)', 
        'color(srgb-linear 0)',
        'color(srgb-linear)',
      ]
    },
    {
      name: 'hsl',
      examples: [
        'hsl(200deg, 50%, 50%)', 
        'hsl(200 50% 50%)',
        'hsla(200deg, 50%, 50%, 50%)', 
        'hsla(200deg, 50%, 50%, .5)', 
        'hsl(200 50% 50% / 50%)',
        'hsl(200 50% 50% / .5)',
        'hsl(0 0% 100%)', 
        'hsl(none none 100%)', 
        'hsl(0 0% 0%)', 
        'hsl(none none 0%)', 
      ]
    },
    {
      name: 'hwb',
      examples: [
        'hwb(200deg 25% 25%)', 
        'hwb(200 25% 25%)',
        'hwb(200 25% 25% / 50%)',
        'hwb(200 25% 25% / .5)',
        'hwb(0 100% 0%)', 
        'hwb(none 100% none)', 
        'hwb(0 0% 100%)', 
        'hwb(none none 100%)', 
      ]
    },
    {
      name: 'lch',
      examples: [
        'lch(58% 32 241deg)',
        'lch(58 32 241deg)',
        'lch(58 32 241)',
        'lch(58 20% 241)',
        'lch(58% 20% 241 / 50%)',
        'lch(58% 32 241 / .5)',
        'lch(100% 0 0)', 
        'lch(100 0 0)', 
        'lch(100 none none)', 
        'lch(0% 0 0)', 
        'lch(0 0 0)', 
        'lch(none none none)', 
      ]
    },
    {
      name: 'oklch',
      examples: [
        'oklch(64% .1 233deg)',
        'oklch(.64 .1 233deg)',
        'oklch(.64 .1 233)',
        'oklch(.64 20% 233)',
        'oklch(64% 20% 233 / 50%)',
        'oklch(64% .1 233 / .5)',
        'oklch(100% 0 0)', 
        'oklch(1 0 0)', 
        'oklch(1 none none)',
        'oklch(0% 0 0)',
        'oklch(0 0 0)',
        'oklch(none none none)',
      ]
    },
    {
      name: 'lab',
      examples: [
        'lab(58% -16 -30)', 
        'lab(58 -16 -30)', 
        'lab(58 -13% -24%)',
        'lab(58% -13% -24% / 50%)', 
        'lab(58% -16 -30 / .5)', 
        'lab(100% 0 0)',
        'lab(100 0 0)',
        'lab(100 none none)',
        'lab(0% 0 0)',
        'lab(0 0 0)',
        'lab(none none none)', 
      ]
    },
    {
      name: 'oklab',
      examples: [
        'oklab(64% -.1 -.1)', 
        'oklab(.64 -.1 -.1)', 
        'oklab(64% -20% -20%)', 
        'oklab(64% -20% -20% / 50%)',  
        'oklab(64% -.1 -.1 / .5)', 
        'oklab(100% 0 0)', 
        'oklab(1 0 0)', 
        'oklab(1 none none)', 
        'oklab(0% 0 0)', 
        'oklab(0 0 0)', 
        'oklab(none none none)', 
      ]
    },
    {
      name: 'display-p3',
      examples: [
        'color(display-p3 34% 58% 73%)',
        'color(display-p3 .34 .58 .73)',
        'color(display-p3 34% 58% 73% / 50%)',
        'color(display-p3 .34 .58 .73 / .5)',
        'color(display-p3 100% 100% 100%)', 
        'color(display-p3 1 1 1)', 
        'color(display-p3 0% 0% 0%)', 
        'color(display-p3 0 0 0)', 
        'color(display-p3 none none none)', 
        'color(display-p3 0)',
        'color(display-p3)',
      ]
    },
    {
      name: 'rec2020',
      examples: [
        'color(rec2020 34% 58% 73%)',
        'color(rec2020 .34 .58 .73)',
        'color(rec2020 34% 58% 73% / 50%)',
        'color(rec2020 .34 .58 .73 / .5)',
        'color(rec2020 100% 100% 100%)', 
        'color(rec2020 1 1 1)', 
        'color(rec2020 0% 0% 0%)', 
        'color(rec2020 0 0 0)', 
        'color(rec2020 none none none)', 
        'color(rec2020 0)',
        'color(rec2020)',
      ]
    },
    {
      name: 'a98-rgb',
      examples: [
        'color(a98-rgb 34% 58% 73%)',
        'color(a98-rgb .34 .58 .73)',
        'color(a98-rgb 34% 58% 73% / 50%)',
        'color(a98-rgb .34 .58 .73 / .5)',
        'color(a98-rgb 100% 100% 100%)', 
        'color(a98-rgb 1 1 1)', 
        'color(a98-rgb 0% 0% 0%)', 
        'color(a98-rgb 0 0 0)', 
        'color(a98-rgb none none none)', 
        'color(a98-rgb 0)',
        'color(a98-rgb)',
      ]
    },
    {
      name: 'prophoto-rgb',
      examples: [
        'color(prophoto-rgb 34% 58% 73%)',
        'color(prophoto-rgb .34 .58 .73)',
        'color(prophoto-rgb 34% 58% 73% / 50%)',
        'color(prophoto-rgb .34 .58 .73 / .5)',
        'color(prophoto-rgb 100% 100% 100%)', 
        'color(prophoto-rgb 1 1 1)', 
        'color(prophoto-rgb 0% 0% 0%)', 
        'color(prophoto-rgb 0 0 0)', 
        'color(prophoto-rgb none none none)', 
        'color(prophoto-rgb 0)',
        'color(prophoto-rgb)', 
      ]
    },
    {
      name: 'xyz',
      examples: [
        'color(xyz 22% 26% 53%)',
        'color(xyz .22 .26 .53)',
        'color(xyz .22 .26 .53 / 50%)',
        'color(xyz .22 .26 .53 / .5)',
        'color(xyz 100% 100% 100%)', 
        'color(xyz 1 1 1)', 
        'color(xyz 0% 0% 0%)', 
        'color(xyz 0 0 0)', 
        'color(xyz none none none)', 
        'color(xyz)', 
      ]
    },
    {
      name: 'xyz-d50',
      examples: [
        'color(xyz-d50 22% 26% 53%)',
        'color(xyz-d50 .22 .26 .53)',
        'color(xyz-d50 .22 .26 .53 / 50%)',
        'color(xyz-d50 .22 .26 .53 / .5)',
        'color(xyz-d50 100% 100% 100%)', 
        'color(xyz-d50 1 1 1)', 
        'color(xyz-d50 0% 0% 0%)', 
        'color(xyz-d50 0 0 0)', 
        'color(xyz-d50 none none none)', 
        'color(xyz-d50)', 
      ]
    },
    {
      name: 'xyz-d65',
      examples: [
        'color(xyz-d65 22% 26% 53%)',
        'color(xyz-d65 .22 .26 .53)',
        'color(xyz-d65 .22 .26 .53 / 50%)',
        'color(xyz-d65 .22 .26 .53 / .5)',
        'color(xyz-d65 100% 100% 100%)', 
        'color(xyz-d65 1 1 1)', 
        'color(xyz-d65 0% 0% 0%)', 
        'color(xyz-d65 0 0 0)', 
        'color(xyz-d65 none none none)', 
        'color(xyz-d65)', 
      ]
    },
  ]

each space in spaces
  dl
    dt= space.name
    each color in space.examples
      dd
        .swatch(style="--_color: " + color)
        code= color
!

CSS 

              
                @import "https://unpkg.com/open-props" layer(design.system);
@import "https://unpkg.com/open-props/normalize.min.css" layer(demo.support);

@layer demo.support;

@layer demo {
  .swatch {
    background: var(--_color, red);
    inline-size: var(--size-3);
    aspect-ratio: var(--ratio-square);
    box-shadow: var(--inner-shadow-0);
    border-radius: var(--radius-1);
  }
}

@layer demo.support {
  body {
    --_grid-wrap: repeat(auto-fill, minmax(min(100%, 320px), 1fr));
    display: grid;
    grid-template-columns: var(--_grid-wrap);
    place-content: center;
    align-items: start;
    padding: var(--size-10);
    gap: var(--size-10);
  }
  
  dl {
    display: grid;
    gap: var(--size-2);
  }
  
  dt {
    text-transform: uppercase;
    font-size: var(--font-size-5);
  }
  
  dd {
    display: flex;
    align-items: center;
    gap: var(--size-2);
  }
  
  @media (prefers-color-scheme: light) {
    body {
      background: var(--gray-4);  
    }
  }
}
!

JS
!
999px

Console