Flow.org is described as 'Flow is a static type checker for JavaScript that we built at Facebook. The overall mission of Flow is to deliver an immersive coding experience for JavaScript developers—a fast edit-refresh cycle—even as the codebase evolves and grows' and is an website in the development category. There are more than 10 alternatives to Flow.org, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac and BSD apps. The best Flow.org alternative is JavaScript, which is both free and Open Source. Other great sites and apps similar to Flow.org are TypeScript, Google Chrome Developer Tools, Firefox Developer Tools and Web Developer.