Pen Settings

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.

Learn more · Versions

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.

!
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.

Learn more · Versions

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 URL's 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 it's URL and the proper URL extention.

Powered by Algolia
About External Resources

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.

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

Learn more

+ add another resource

JavaScript

About JavaScript Preprocessors

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

Learn more · Versions

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.

Powered by Algolia
About External Resources

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.

Learn more

+ add another resource

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.

Powered by Algolia
About Packages

Using packages here is powered by Skypack, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ES6 import 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.

Behavior

Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML 

              
                <article>
  <h1>Pure CSS reading position indicator</h1>
  <p>Plenty of bugs in both Chrome and Safari, but when those are worked out this would be a simple solution to adding a trail to what you have scrolled past to your scrollbar marking progress along an article natively without JS. What are the bugs? As of February 28, 2016 Chrome removes 50% of the tail when scrolling past 50% and Safari doesn’t hide scrollbar styling overflow from the box shadow.</p>
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Non earum quisquam dolorum distinctio voluptates quaerat dignissimos suscipit expedita ad accusamus, iusto delectus a, quas at ex veritatis nesciunt? Aspernatur, eius!</p>
  <p>Veritatis pariatur eligendi repellendus dolor sed magnam nulla laboriosam necessitatibus beatae dolorem, minus explicabo laudantium ut saepe, vero rem nostrum possimus ex qui, aspernatur doloremque? Sapiente corporis, assumenda iure exercitationem.</p>
  <p>A tempora cupiditate totam sint omnis iure ea. Earum nam libero impedit! Error est officiis minus cupiditate amet, repellendus, cumque incidunt velit. Hic magnam veritatis reiciendis, iste nostrum numquam pariatur!</p>
  <p>Quisquam magnam vel cum quidem enim illum aperiam ducimus fugit, consequatur harum maiores at, neque dolores temporibus odit beatae minima nisi nesciunt mollitia amet animi magni laudantium alias! Ipsum, ipsa!</p>
  <p>Repudiandae praesentium, fugit at expedita cupiditate corrupti illum molestias, magnam similique soluta id molestiae temporibus eos veritatis, numquam quas modi. Velit veritatis, at voluptatum dolore cupiditate? Blanditiis excepturi delectus veniam.</p>
  <p>Commodi repellendus blanditiis reprehenderit nulla, quisquam, maiores voluptate ex laboriosam odit similique praesentium reiciendis, asperiores velit id voluptatum fugit dolore esse facere sequi nemo nobis doloribus itaque corrupti? Vero, excepturi?</p>
  <p>Voluptatem corporis eveniet laborum consectetur, voluptatum repellat saepe fugit, aspernatur eligendi, veritatis ea temporibus ipsa, expedita rem fugiat perspiciatis accusantium consequuntur necessitatibus vitae rerum! Qui rem dolores accusamus consequatur odio.</p>
  <p>Quibusdam dolor, vitae at perspiciatis commodi provident deleniti excepturi nobis et ipsam eligendi aperiam eum nam a vel culpa, quidem velit molestias recusandae perferendis praesentium distinctio! Incidunt alias, ad itaque.</p>
  <p>Voluptatem, magni eaque laudantium facilis reprehenderit non quibusdam natus temporibus impedit suscipit, perferendis labore inventore commodi, qui est, quas harum asperiores! Labore aspernatur, tempora illo nulla rem. Obcaecati, quaerat laboriosam?</p>
  <p>Minima nesciunt tenetur est iure architecto, exercitationem fugit mollitia! Tempore ad molestiae, eos voluptatum deserunt, architecto, magnam deleniti in fuga libero cum ut? Nulla neque, adipisci odio doloremque reiciendis vero!</p>
  <p>Esse beatae sit doloribus. Eveniet libero tenetur quae officia, placeat ab, voluptatibus amet quos dicta, beatae, odit. Et dolores sit explicabo, ipsum ut ipsa consequuntur, similique nam rerum culpa fuga?</p>
  <p>Ipsa nulla blanditiis mollitia dolor repellat quas incidunt omnis quae possimus, aliquid, ullam at pariatur alias nostrum voluptate aperiam ut eligendi, obcaecati architecto, dignissimos veritatis saepe tenetur! Quae asperiores, molestias!</p>
  <p>Eligendi alias praesentium labore voluptas neque reprehenderit maxime odit repellendus beatae veritatis ipsa molestias, et iusto minus tempore est, provident repudiandae fuga voluptatibus in nihil sequi quisquam odio. Mollitia, id.</p>
  <p>Cumque error debitis repudiandae, natus fugit ipsam quia voluptatem ut dolorem maiores placeat totam dolor non in ducimus eius eum, ab exercitationem. Eligendi aliquid est eaque ducimus, quibusdam aut ex!</p>
  <p>Qui assumenda accusantium cumque illum recusandae modi dolores, velit adipisci, unde quam doloremque voluptates sunt hic placeat nemo delectus facere ex natus, ipsa, tempore a nihil molestiae. Modi, dolores labore!</p>
  <p>Iusto reiciendis amet, similique eaque harum qui, vero, quos facere natus dolorem at commodi eveniet numquam ab labore, voluptas alias mollitia odio exercitationem debitis. Aperiam porro ratione odit ipsa rerum.</p>
</article>
!

CSS 

              
                body::-webkit-scrollbar {
  width: 6px;
}
 
body::-webkit-scrollbar-track {
  overflow: hidden;
  background-color: #ddd;
}
body::-webkit-scrollbar-thumb {
  background-color: #ff4f1f;
  box-shadow:
    0 -100vh 0 100vh #ff4f1f;
}

article {
  max-width: 40em;
  margin: auto;
  padding: 10vw 5% 50vh;
  font-size: 18px;
  color: #333;
}
h1 {
  font-style: italic;
}
!

JS
!
999px

Console