Codepen
CodePen is a social development environment for front-end designers and developers. Build and deploy a website, show off your work, build test cases to learn and debug, and find inspiration.
Code SandBox
A sandbox is a testing environment that isolates untested code changes and outright experimentation from the production environment or repository, in the context of software development including Web development and revision control.
Gitpod
Dev Environments Built for the Cloud. Describe your dev environments as code and automate the last missing piece in your DevOps pipeline.
SoloLearn
SoloLearn: Learn to code for FREE! courses; code playground; Discuss; top learners; blog; sign in. Learn to code for free! Interactive lessons, ‘on-the-go’ practice, peer support. Start Learning Now! I already have an account Python 3 Learn Python, one of today’s most in-demand programming languages on-the-go!