1. Codepen is front-end only, whereas hyperdev runs back-end code as well (node.js) 2. Codepen gives you 1 html, 1 css, and 1 js file per pen... hyperdev lets

1. Codepen is front-end only, whereas hyperdev runs back-end code as well (node.js) 2. Codepen gives you 1 html, 1 css, and 1 js file per pen... hyperdev lets you have as many front-end and back-end files as you want. (Technically you can have multiple files in a codepen by linking to them, but it's not the primary use-case and is not as in-your-face as hyperdev is).