- embedresponsively.com helps build responsive embed codes for embedding rich third-party media into responsive web pages. — embedresponsively.com
- dabblet is an interactive playground for quickly testing snippets of CSS and HTML code — dabblet
- An online tool to display formatted source code — Syntax Highlighting
- CodePen is all about front end code inspiration, education, and sharing. Enter HTML, CSS, and JavaScript and the combined result is displayed below. – CodePen
- JSFIDDLE
- JSDB.io is a collection of the best javascript libraries
- DevDocs combines multiple API documentations in a fast, organized, and searchable interface.