HTML Editor

Write your code in the HTML, CSS and JavaScript tabs, and the preview next to them shows the page as you type. Untick “Update as I type” to run the code only when you click “Run” or press Ctrl+Enter. The editor highlights the code, indents new lines, closes brackets and tags and marks errors in the margin, and the console under the preview shows what your script writes with console.log() and the errors it throws, with their line numbers. The buttons above the preview show the page at the width of a laptop, a tablet or a phone, and the full screen button gives the editor the whole window.

Your page runs in a separate, sandboxed frame, so its styles and scripts cannot change this site, and the site does not read your code. The code is saved in your browser as you type and is still there when you open the editor again. “Copy HTML” and “Download HTML” give you the whole page as one HTML file with the CSS and JavaScript inside, ready to open in a browser or to upload, and “Open a file” loads an HTML, CSS or JavaScript file into its tab. “Load the example” brings back the sample page. The editor is built on Ace, an open source code editor.