Colaboratory is described as 'free Jupyter notebook environment that requires no setup and runs entirely in the cloud. With Colaboratory you can write and execute code, save and share your analyses, and access powerful computing resources, all for free from your browser' and is an website in the Development category. There are four alternatives to Colaboratory, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac and Chrome OS. The best alternative is Jupyter, which is both free and Open Source. Other great sites and apps similar to Colaboratory are Jupyterlab (Free, Open Source), Paperspace (Paid) and CoCalc (Free, Open Source).