# dafny-lang/dafny

Dafny is a verification-aware programming language

Repository: https://github.com/dafny-lang/dafny
Canonical: https://ross.abutalabs.com/products/dafny
Homepage: https://dafny.org
Language: C#
License: NOASSERTION
License Family: other
Topics: programming-language, verification
Last push: 2026-08-25T10:26:52+00:00

## Health v2 (maintenance only)
Score: 76/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 99, release rhythm 32, longevity 100
- inputs: {"age_days": 3791, "days_push": 8, "days_rel": 373, "gap_med": 48.5, "n_releases_24m": 5}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3516, forks 326 (observed 2026-08-28T04:08:07.852376+00:00)

## What it is
Dafny is a verification-aware programming language with native support for writing specifications and a built-in static verifier powered by SMT solving (Z3). It compiles verified code to C#, Go, Python, Java, or JavaScript and ships with IDE plugins, a language server, and a formatter.

## Use cases
- write provably correct code against formal specifications
- verify algorithms with pre/postconditions and loop invariants
- teach formal methods and program verification in courses
- catch specification violations before runtime instead of relying on tests
- compile verified code to C#, Java, Go, Python, or JavaScript
- construct mathematical proofs about software with lemmas and calculational proofs

## When to choose
- you need high assurance that code meets its specifications
- you are teaching or learning formal verification
- you are building safety- or correctness-critical algorithms
- you want verification integrated into your editor as you type

## When to avoid
- you need a general-purpose language with a large ecosystem and libraries
- your team has no experience with formal specifications
- you need fast iteration without verification overhead
- you target platforms outside the supported compilation backends

## Facets
- artifact type: cli-tool
- maturity: active
- function: programming-language, compiler, interpreter, type-system, developer-tools
- domain: programming-languages, compilers, developer-tools, education
- platform: windows, cross-platform, cli, editor-plugin, dotnet
- tags: formal-verification, static-verification, smt-solver, z3, specification-language, proof-assistant, transpilation, lsp, programming-language, algorithms, macos, linux

## Member repositories
- dafny-lang/dafny (main) score 76

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:07.852376+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T08:31:29.659746+00:00, confidence not recorded.
  - readme: https://github.com/dafny-lang/dafny (fetched 2026-08-28T04:08:07.852376+00:00, sha e44a2e855e1a)
  - homepage: https://dafny.org (fetched 2026-08-29T09:29:24.729685+00:00, sha 4e70d2680887)
  - site_page: https://dafny.org/latest/Installation (fetched 2026-08-29T09:29:24.732384+00:00, sha c8fb016ac7dd)
  - site_page: https://dafny.org/Snapshots (fetched 2026-08-29T09:29:24.734595+00:00, sha 99797549a6b8)
- Data as of 2026-08-30T08:39:29.467469+00:00.