# reasonml/reason

Simple, fast & type safe code that leverages the JavaScript & OCaml ecosystems

Repository: https://github.com/reasonml/reason
Canonical: https://ross.abutalabs.com/products/reason
Homepage: http://reasonml.github.io
Language: OCaml
License: MIT
License Family: permissive
Topics: ocaml, javascript, reasonml, reason, programming-language
Last push: 2026-08-13T01:01:23+00:00

## Health v2 (maintenance only)
Score: 91/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 97, release rhythm 78, longevity 100
- inputs: {"age_days": 3943, "days_push": 21, "days_rel": 71, "gap_med": 63.0, "n_releases_24m": 9}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 10323, forks 436 (observed 2026-08-28T04:10:41.614652+00:00)

## What it is
Reason is an alternative syntax and toolchain for the OCaml programming language, offering simple, fast, type-safe code with a JavaScript-friendly surface. It includes the refmt formatter and compiles to native or JavaScript (via Melange), leveraging both the OCaml and JavaScript ecosystems.

## Use cases
- write type-safe code with OCaml semantics but friendlier syntax
- compile OCaml-like code to JavaScript
- format Reason source files with refmt
- learn functional programming with strong type inference
- build web frontends using OCaml ecosystem libraries

## When to choose
- you want OCaml's type system with a simpler, JS-like syntax
- you are maintaining an existing Reason/ReasonReact codebase
- you want to target both native OCaml and JavaScript from one language

## When to avoid
- you are starting a new project today - ReScript or plain OCaml are more actively developed
- you need a large ecosystem of language tooling and community support
- you want dynamic typing or rapid prototyping without type constraints

## Facets
- artifact type: library
- maturity: maintenance
- function: programming-language, compiler, formatter, type-system
- domain: programming-languages, compilers, web-development, developer-tools
- platform: cross-platform, cli
- tags: reasonml, ocaml-syntax, melange, refmt, alt-syntax, functional-programming, type-safe, javascript, ocaml, nodejs

## Member repositories
- reasonml/reason (main) score 91

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:10:41.614652+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 2026-08-29T17:19:10.345358+00:00, confidence not recorded.
  - readme: https://github.com/reasonml/reason (fetched 2026-08-28T04:10:41.614652+00:00, sha bf72ca4e41c2)
  - homepage: http://reasonml.github.io (fetched 2026-08-29T08:18:27.997523+00:00, sha 0eb3eccca1aa)
- Data as of 2026-08-30T08:39:29.467469+00:00.