Build, share, and learn JavaScript, CSS, and HTML with our online code editor.

The big idea is that you can "break ... Project editor. Live View is a URL to see a real-time updating preview of your code that you can use for whatever you like. This is particularly useful for cross-browser and cross-device testing. Your changes are injected automatically and instantly.

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor.

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor.

April 16, 2020 - Live View is a full-page view of your Pen that updates in real time as you update the code in your Pen. Updates happen as you type, just like the preview in the Editor, except that this URL can be open in another window or tab, in a different ...

April 16, 2020 - Editor View is the main view of a Pen on CodePen. It contains: The HTML editor The CSS editor The JS editor The Live Preview Pen Settings You can create, edit, and save Pens from here.

November 5, 2025 - As you work in the CodePen editor, the build process produces a live preview you can see (we'll just call that the "Preview"). That's at the heart of what CodePen does! The preview has a non-changing URL like: https://[lots_of_letters_and_numbers].pens.io/ Cache Busting The URL of the preview stays the same as you update the Pen.

A client-side live code editor for HTML, CSS, and JavaScript, inspired by CodePen.

This is a simple web based code editor. Click on the menu items on the top and write pure HTML, CSS and JavaScript. Click the 'Run' Button and see the ...

I wanted a lightweight editor where I could see my changes in real time. ...

CodePen doesn't work very well without JavaScript · We're all for progressive enhancement, but CodePen is a bit unique in that it's all about writing and showing front end code, including JavaScript. It's required to use most of the features of CodePen · Need to know how to enable it?

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor.

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor.

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor.

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor.

Edit Pen · {"__browser":{"country":"US","device":"unknown_device","mobile":false,"name":"chrome","platform":"unknown_platform","version":"537"},"__constants":{},"__CPDATA":{"domain_iframe":"https://cdpn.io","environment":"production","host":"codepen.io","iframe_allow":"accelerometer *; bluetooth ...

Markdown editor with live preview and compiled HTML code...

Fully responsive webpage clone of "CodePen" code editor designed with HTML, CSS and JavaScript. Live: https://mdrasen.github.io/Codepen-Code-Editor-2.0/

June 13, 2025 - Online code editors like CodePen, JSFiddle, and VSCode Online have revolutionized how developers write, test, and share code. But have you ever wondered how they work? In this step-by-step guide, we’ll build a fully functional browser-based code editor with: ✅ Real-time syntax highlighting (like VS Code) ✅ Live preview (HTML/CSS/JS execution) ✅ File saving & loading (using IndexedDB or localStorage) ✅ Monaco Editor integration (the powerhouse behind VS Code)