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Documenting everything about OCaml


Code Tools

Editor Tools

For an OCaml beginner, the recommended editor of choice is Visual Studio code with the ReasonML plugin. See editor setup.

Visual Studio Code

  • VSCode-Reason: The Reason/OCaml plugin for Visual Studio Code. Allows for all the advantages provided by Merlin with the convenience of the VSCode IDE.
  • VSCode-OCaml-platform: in-development. OCaml extension for Visual Studio Code.


  • tuareg: OCaml mode for Emacs that can run the toplevel and the debugger within Emacs.

Sublime Text


  • Vim only really needs merlin, and optionally, ocp-indent or ocamlformat.


  • Neovim supports plugins written in any language, including OCaml using the vcaml package.


  • user-setup: automatically configures several editors to use merlin, ocp-indent, and ocp-index if they are installed. Run opam install user-setup to install it, and then follow the instructions, which tell you to run opam user-setup install.
  • merlin: the main tool used to provide information to editors about OCaml codebases. Note that to provide information, the code must first be compiled. Dune is able to automatically create /.merlin/ files, which are needed to help merlin find the compiled files.
  • ocp-index: Easy access to the interface information of installed OCaml libraries. Contains a few standalone tools:
    • ocp-browser: Excellent, easily accessible ncurses-based API and documentation browser. Available independently on OPAM.
    • ocp-index-top: toplevel directive for looking up documentation using ocp-index.
  • ocp-indent is a coding style formatting tool that relies on heuristics and partial parsing rather than a full end-to-end parsing and printing approach, like ocamlformat below. The advantage of ocp-indent’s approach is that even partially-compiling files can be indented, as can code fragments.
  • ocamlformat is a comprehensive coding style formatting tool that parses the code and prints it out again. This follows the example of the refmt tool for Reason. While new, ocamlformat may eventually overtake ocp-indent.

Development Tools

  • utop: Very powerful toplevel for OCaml, that is far better than the default one. A must-install for every OCaml programmer.
  • Online tool for playing around with OCaml (most up-to-date version).
  • odoc: An automatic documentation generator for OCaml that creates beautiful html.
  • Try OCaml: Try OCaml in your web browser.
  • codingground: Compile and execute OCaml code online.
  • mdx: Tool for executing code or shell snippets inside markdown files.
  • iocaml: An OCaml kernel for the IPython notebook.
  • ghim: A command-line tool to manage Github Issues.
  • OCaml Yeoman Generator: Yeoman generator to scaffold OCaml modules.
  • Dead Code Analyzer: OCaml dead code analysis.

Code Coverage