CodePen is a communal front-end development platform providing real-time HTML, CSS, and JavaScript previews. Users can build projects, test code, and enhance skills through challenges. Features include Presentation Mode for conferences and a vast active community for sharing and discovery.
Cost / License
- Freemium (Subscription)
- Proprietary
Application types
Platforms
- Online




CodePen is the most popular Web-based alternative to ShiftEdit.
CodePen is the most popular free alternative to ShiftEdit.
- CodePen is Freemium and Proprietary















































It's like a virtual box embedded in a browser. Vou van even run vim inside their terminal emulator (well, you can't use any Ctrl-W or Ctrl-Q shortcut...) C9.io team is the one who created the ACE editor. And here we can see it at its fullest power, with vim mode and sublime-like UI. Truly awesome, you can setup a development web server and run the app (PHP, Python, Ruby, you name it), Almost like having a hosted virtual machine (which is what it is, in fact...)