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What is SAFE?

The SAFE stack is the best way to write functional-first web applications.

The SAFE stack allows you to develop web applications almost entirely in F#, without needing to compromise and shoehorn your codebase into an object-oriented framework or library, and without needing you to be an expert in CSS or HTML to create compelling, rich client-side web applications. SAFE Stack is:

  • Open-source
  • Free
  • Type-safe
  • Flexible
  • Cloud-ready

The SAFE stack is made up of four components:

  • A web server running on .NET Core for hosting back-end services in F#
  • A hosting platform that provides simple, scalable deployment models plus associated platform services for application developers
  • A mechanism to run F# in the web browser for client-side delivery of F#
  • An F# programming model for client-side user interfaces


SAFE provides developers with a simple and consistent programming model for developing rich, scalable web-enabled applications that can run on multiple platforms. SAFE takes advantage of F#'s functional-first experience backed by the powerful and mature .NET framework to provide a type-safe, reliable experience that leads to the "pit of success".

  • Create client / server applications entirely in F#
  • Re-use development skills on client and server
  • Rapidly create rich client-side web applications with no Javascript knowledge
  • Runs on the latest .NET Core (and tested daily by Microsoft)
  • Rapid development cycle with support for hot module replacement
  • Interact with native Javascript libraries whenever needed
  • Create client-side applications purely in F#, with full type checking for safety
  • Seamlessly share code between client and server