Article · Wikipedia archive · Last revised Jul 12, 2026

F* (programming language)

F* is a high-level, multi-paradigm, functional and object-oriented programming language inspired by the languages ML, Caml, and OCaml, and intended for program verification. It is a joint project of Microsoft Research, and the French Institute for Research in Computer Science and Automation (Inria). Its type system includes dependent types, monadic effects, and refinement types. This allows expressing precise specifications for programs, including functional correctness and security properties. The F* type-checker aims to prove that programs meet their specifications using a combination of satisfiability modulo theories (SMT) solving and manual proofs. For execution, programs written in F* can be translated to OCaml, F#, C, WebAssembly, or assembly language. Prior F* versions could also be translated to JavaScript.

Last revised
Jul 12, 2026
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F*
The official F* logo
ParadigmMulti-paradigm: functional, imperative
FamilyML: Caml: OCaml
Designed byNikhil Swamy, Juan Chen, Cédric Fournet, Pierre-Yves Strub, Karthikeyan Bhargavan, Jean Yang
DevelopersMicrosoft Research,
Inria1
First appeared2011 (2011)
Stable release
v2026.04.172 / 18 April 2026 (2026-04-18)
Typing disciplinedependent, inferred, static, strong
Implementation languageF*
OSCross-platform: Linux, macOS, Windows
LicenseApache 2.0
Filename extensions.fst
Websitefstar-lang.org
Influenced by
Dafny, F#, Lean, OCaml, Rocq, Standard ML

F* (pronounced F star) is a high-level, multi-paradigm, functional and object-oriented programming language inspired by the languages ML, Caml, and OCaml, and intended for program verification. It is a joint project of Microsoft Research, and the French Institute for Research in Computer Science and Automation (Inria).1 Its type system includes dependent types, monadic effects, and refinement types. This allows expressing precise specifications for programs, including functional correctness and security properties. The F* type-checker aims to prove that programs meet their specifications using a combination of satisfiability modulo theories (SMT) solving and manual proofs. For execution, programs written in F* can be translated to OCaml, F#, C, WebAssembly (via KaRaMeL tool), or assembly language (via Vale toolchain). Prior F* versions could also be translated to JavaScript.

It was introduced in 201134 and is under active development on GitHub.2

History

Versions

Until version 2022.03.24, F* was written entirely in a common subset of F* and F# and supported bootstrapping in both OCaml and F#. This was dropped starting in version 2022.04.02.56

Overview

Operators

F* supports common arithmetic operators such as +, -, *, and /. Also, F* supports relational operators like <, <=, ==, !=, >, and >=.7

Data types

Common primitive data types in F* are bool, int, float, char, and unit.7

References

References

  1. "Microsoft Research Inria Joint Centre". MSR-INRIA.
  2. "FStarLang/FStar". GitHub. Archived from the original on 26 April 2026. Retrieved 26 April 2026.
  3. Swamy, Nikhil; Chen, Juan; Fournet, Cédric; Strub, Pierre-Yves; Bhargavan, Karthikeyan; Yang, Jean (September 2011). Secure distributed programming with value-dependent types. ICFP '11: Proceedings of the 16th ACM SIGPLAN International Conference on Functional Programming. Vol. 46. Tokyo, Japan: Association for Computing Machinery. pp. 266–278. doi:10.1145/2034574.2034811. Retrieved 17 April 2023.
  4. "The F* Project". Microsoft. Retrieved 20 April 2023.
  5. "fstar.exe is no longer buildable in F# as a .NET executable #2512". Github. Retrieved 17 April 2023.
  6. "Consider dropping requirement that F* code has to be valid F# #1737". Github. Retrieved 17 April 2023.
  7. Swamy, Nikhil; Martínez, Guido; Rastogi, Aseem (Jan 14, 2024). Proof-Oriented Programming in F* (PDF).

Sources

  • Ahman, Danel; Hriţcu, Cătălin; Maillard, Kenji; Martínez, Guido; Plotkin, Gordon; Protzenko, Jonathan; Rastogi, Aseem; Swamy, Nikhil (2017). "Dijkstra Monads for Free". 44nd ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages.
  • Swamy, Nikhil; Hriţcu, Cătălin; Keller, Chantal; Rastogi, Aseem; Delignat-Lavaud, Antoine; Forest, Simon; Bhargavan, Karthikeyan; Fournet, Cédric; Strub, Pierre-Yves; Kohlweiss, Markulf; Zinzindohoue, Jean-Karim; Zanella-Béguelin, Santiago (2016). "Dependent Types and Multi-Monadic Effects in F*". 43nd ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages.
  • Swamy, Nikhil; Martínez, Guido; Rastogi, Aseem (2024). Proof-Oriented Programming in F*.
External links