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Reason

A syntax and toolchain for OCaml that lets you write type-safe code for the JavaScript and OCaml ecosystems.

GitHub Download 3.18.0
Stars
10.3k
Forks
437
Licence
MIT
Language
OCaml
Last update
1 months ago
Type
Dev tool

What it is

Reason is a programming toolchain built on OCaml that offers a different syntax, closer to JavaScript, for writing type-safe code. The README describes it as simple, fast, and type safe, and says it works with both the JavaScript and OCaml ecosystems. This repository contains the compiler and formatting tooling; the user documentation lives on the project's website.

  • Write typed application code that compiles through the OCaml toolchain
  • Use the Reason formatting and syntax tooling to convert or format code (per the project's docs)
  • Contribute to the Reason compiler by running its test suite

Great for

  • Developers who already know JavaScript and want static types without leaving a familiar-looking syntax
  • OCaml developers who prefer a JavaScript-like surface syntax
  • Teams looking into compiling typed code to JavaScript via the OCaml ecosystem
  • Contributors who want to work on the Reason compiler itself

Not ideal for

  • Beginners looking for a first programming language, since it sits on top of OCaml and its tooling
  • Anyone who needs a stable, widely used ecosystem, as the README does not describe adoption or maturity levels
  • Projects that cannot take on the OCaml toolchain as a dependency
Step-by-step guide: how to use ReasonInstall, first run, examples, tips and FAQs

How to get it

  1. 1

    Clone and build from source

    You'll need: npm (for installing esy)

    Install esy (contributor setup)

    npm install -g esy@next

    Clone the repository

    git clone https://github.com/reasonml/reason.git

    Enter the repository directory

    cd reason

    Build the project

    esy
  2. 2

    Run it

    • Install esy with npm as shown in the README
    • Clone the repository and change into its directory
    • Run esy to build the project
    • Run esy test to execute the test suite
  3. 3

    Get the most out of it

    • Read the Getting Started guide on the Reason website for user-level setup
    • Check the docs/ directory for contributor documentation
    • Use the community Discord linked in the README to ask questions

Downloads

Source code (.zip)master branch · straight from GitHubRelease 3.18.01 files incl. reason-3.18.0.tbzOfficial website & docsreasonml.github.io

Strengths

  • Type-safe code with a syntax many JavaScript developers find easier to read than standard OCaml
  • Builds on the established OCaml ecosystem rather than replacing it
  • Open source under the MIT license with an active repository

Trade-offs

  • Requires understanding of OCaml tooling and concepts, which adds a learning curve
  • The README is short and points to external docs for most user-facing guidance
  • Install and contributor setup use esy, a less common tool that may need extra learning

How it compares

ProjectStarsTypeLevelUpdatedBest for
reason (this)10.3kDev tooladvanced1 months agoDevelopers who already know JavaScript and want static types without leaving a familiar-looking syntax
julia49.2kOtherintermediate4 days agoScientists and engineers who write numerical code and want readable syntax with good speed
v38.1kOtherintermediate4 days agoDevelopers who want to try a compact compiled language with a short learning curve
wenyan20.3kOtherbeginner3.0 years agoDevelopers curious about non-English programming languages
learn-python18.5kLearning resourcebeginner7 months agoBeginners who want to learn Python syntax by reading and running examples

Stats synced from GitHub. The assessment above was drafted with AI from the project's README on 2026-10-29 and may miss recent changes — check the README before relying on a command. MIT licence: free to use, modify and distribute, including commercially, as long as you keep the copyright notice.