JSFiddle.net and CodePen.io are both online HTML-CSS-JavaScript playgrounds to easily test your code. They are both free and don’t require registration. Just add your code and hit the Run button to test it, then Save it to generate a custom URL with your snippets.
JSFiddle is an easy to use, free tool where you can test HTML – CSS – JavaScript in an online interface. Run and save your code and use the custom URL to access it anytime. To make adjustments to the code, simply hit the Save button and the software will record changes increasing the version variable in the link.
To demonstrate how to use it we have created a HTML CSS JavaScript Progress Bar and added the short code to JSFiddle: jsfiddle.net/guh0mf0d/1/
Codepen.io is another popular code playground to experiment, easily save and share web code with. This is the very same progress bar code saved with Codepen: codepen.io/anon/pen/KdBBzN
Apart from the two most popular editors above we can mention cssdeck.com or liveweave.com. Knowing about these online tools you no longer have to copy all documents in one file to share it with somebody.