Web-Maker is a chrome extension that converts your Chrome tabs into an offline playground for your web experiments.
We get asked fairly often about an offline version of CodePen. While we think that would be cool, in all honesty, we aren't particularly close to that. If you're looking for a CodePen-like offline editor, and use Chrome, check out Web-Maker by Kushagra Gour.
It replaces your "New Tab" window with a code editor (you can also open it anytime from the Chrome menu). It's not quite 1-for-1 with CodePen editor features, but it has a surprising number of them. Plus, you can click a button to send it over to CodePen if you ultimately want your creation here.