F*
Hacker ApprovedRanked 4 of 4 verification languages by recommenders
People recommend it for proof-oriented programming with a powerful type system and real-world verified code. Critics say it can be slow and hard to use for complex software.
People recommend it for proof-oriented programming with a powerful type system and real-world verified code. Critics say it can be slow and hard to use for complex software.
20 people gave an opinion
- recommend it
- 17
- criticize it
- 3
- approval share
- 85%
Recommended in 7 of 13 months
- November 2025: recommended
- December 2025: recommended
- January 2026: not recommended
- February 2026: recommended
- March 2026: not recommended
- April 2026: recommended
- May 2026: recommended
- June 2026: not recommended
- July 2026: not recommended
- August 2026: recommended
- September 2026: recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it carries the badge
- 17 people recommend itNeeds 10 or more, met.
- 5.7 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 7 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Software-focused alternative to Lean and Isabelle
“proof-oriented alternative to Isabelle that is focused on software verification”
Comment from 19 Feb 2026 in “Learning Lean: Part 1” “a much better choice for proof-oriented programming than lean4”
Comment from 13 Apr 2026 in “A Perfectable Programming Language” “competes directly with Lean but is more guided towards SWE”
Comment from 27 Apr 2026 in “"Why not just use Lean?"” - Comment from 21 Feb 2026 in “Lean 4: How the theorem prover works and why it's the new competitive edge in AI”
Familiar syntax, similar to F#
“I don't find F* syntax anymore intimidating than Haskell, Scala, Mercury, Prolog, etc.”
Comment from 2 Aug 2026 in “F*: A general-purpose proof-oriented programming language” “F# for high-level, and F* Low* for theorem proving and low-level coding”
Comment from 13 Apr 2026 in “A Perfectable Programming Language” “F* looks a lot like F# code with semantics you should be familiar with”
Comment from 2 Aug 2026 in “F*: A general-purpose proof-oriented programming language” Used in real-world and embedded verification
“F* is being used on embedded and in other realworld apps where formal verification is necessary or highly advantageous”
Comment from 25 Nov 2025 in “APT Rust requirement raises questions” “They actually wrote a whole verified TLS implementation in F*”
Comment from 2 Aug 2026 in “F*: A general-purpose proof-oriented programming language” Powerful type system, expressive semantics
“the metatheory is also expressive enough that your source language can be pretty wild with your denotational semantics”
Comment from 3 Aug 2026 in “F*: A general-purpose proof-oriented programming language” “It has a very powerful type system”
Comment from 16 Dec 2025 in “Memory Safety in C# vs. Rust”
What people warn about
Each mark is one comment
Slow and hard for complex software
“trade off a lot of performance to the point that it makes them practically unusable”
Comment from 18 Sep 2026 in “Bend 2 and the Vibe-Coding Trap” “They're really not fun to try and make complex software with”
Comment from 13 Apr 2026 in “A Perfectable Programming Language”
Other verification languages people recommend
The three most recommended other verification languages, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
See all 4 verification languages, rankedWhat people said
23 of the 26 comments that mention it, newest first. Each links to the original comment.
“might get you to what you're looking for”
“trade off a lot of performance to the point that it makes them practically unusable”
“tooling that allows code generation based on the formal proofs like FStart or Dafny”
“they are good, but they and Rust simply don't have the real world legacy”
“the metatheory is also expressive enough that your source language can be pretty wild with your denotational semantics”
“my gripe with the homepage as well in lacking this concise yet powerful example”
“They actually wrote a whole verified TLS implementation in F*”
“I don't find F* syntax anymore intimidating than Haskell, Scala, Mercury, Prolog, etc.”
“This in my opinion gives you a first rough idea for what kind of problems people are using F*.”
“F* looks a lot like F# code with semantics you should be familiar with”
“seems to be a collection of like five different languages and proof systems”
“I liked being able to express calling external libraries while incrementally migrating existing C codebases to F*”
“other languages that follow a stricter/larger compile time regimen e.g. Haskell, OCaml, Idris, ATS, F* would be suitable as well for this kind of approach”
“competes directly with Lean but is more guided towards SWE”
“They're really not fun to try and make complex software with”
“F# for high-level, and F* Low* for theorem proving and low-level coding”
“a much better choice for proof-oriented programming than lean4”
“Dafny and F* are two good showcases”
“proof-oriented alternative to Isabelle that is focused on software verification”
“It has a very powerful type system”
“you're going to use a serious programming language like F*”
“F* is being used on embedded and in other realworld apps where formal verification is necessary or highly advantageous”
“it seems quite nice from a usability perspective”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.