August 2, 2026
Proof? Or it didn’t compile
F*: A general-purpose proof-oriented programming language
A super-serious coding language arrives, and the crowd instantly asks: cool, but where’s the demo
TLDR: F* is a serious open-source language for writing extra-trustworthy software, and its code already helps protect major real-world systems. But the community’s big reaction was less “wow” and more “show us the syntax already,” with jokes, confusion, and even a pronunciation squabble stealing the spotlight.
A new spotlight is on F*, an open-source programming language backed by Microsoft Research, Inria, and its wider community. The pitch is ambitious: write software in a way that helps prove it works correctly, then send that code out to places like OCaml, C, WebAssembly, and even assembly. That sounds wildly impressive on paper — and in real life, F* already feeds security tools used by Firefox, the Linux kernel, Python, Azure, and more. In other words: this is not a toy.
But the comments? Absolutely not in a mood to be dazzled by credentials alone. The loudest reaction was basically: “Great, now show me the actual language.” One frustrated reader complained they clicked through page after page without finding a single code example, comparing the site to a video game homepage with no screenshots. Ouch. Another commenter said F* feels like “five different languages and proof systems” mashed together, which is the kind of line that lands like a roast and a genuine usability critique at the same time.
Still, it wasn’t all doom-posting. One supporter praised F* for helping migrate old C projects bit by bit while still talking to external libraries — a very practical thumbs-up. Another asked if it could be used to build compilers and prove things about them, hinting at the nerdy dream scenario. And then, in peak comment-section fashion, a mini-drama broke out over the pronunciation: yes, people really stopped to argue whether “F*” is pronounced “F star,” despite the website literally saying so. The language may be about proofs, but the community remains committed to proving each other wrong first.
Key Points
- •F* is presented as a proof-oriented programming language that combines dependent types with SMT-based automation and tactic-based theorem proving.
- •F* compiles to OCaml by default and supports extraction to F#, C, Wasm, and assembly through tools such as KaRaMeL and Vale.
- •The project is open source under Apache 2.0 and is actively developed by Microsoft Research, Inria, and the community.
- •The article highlights community resources including installation options, an online book, Low* tutorials, course materials, GitHub Discussions, Zulip, and the F* PoP Up Seminar.
- •F* is used in projects such as Project Everest, HACL*, ValeCrypt, EverCrypt, and EverParse, with production deployments cited in Firefox, the Linux kernel, Python, Hyper-V, Azure, and other systems.