Runnable is described as 'helps you ship faster by freeing the burden of managing dev environments and reducing your dependence on the staging server. Every branch gets it's own full-stack environment, and stays up to date with every git push' and is an website in the Development category. There are five alternatives to Runnable, not only websites but also apps for a variety of platforms, including Self-Hosted solutions, SaaS, Mac and Windows. The best alternative is AWS Cloud9. It's not free, so if you're looking for a free alternative, you could try Ideone or Monaca. Other great sites and apps similar to Runnable are CodePicnic (Freemium) and Dockup (Paid).
AWS Cloud9 is a code editor and development environment built with browser technology yet with the power of a desktop IDE. It's available both as an online service and as a locally hosted platform. FEATURES - Full featured Linux terminal built in.
Monaca makes the hybrid mobile app development process with PhoneGap/Cordova simpler and stress-free with our comprehensive cloud-powered app development tools and services. Monaca can easily be plugged into your existing workflow.