A generic swappable back-end for JSON handling.
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MultiJSON Build Status Dependency Status

Lots of Ruby libraries parse JSON and everyone has their favorite JSON coder. Instead of choosing a single JSON coder and forcing users of your library to be stuck with it, you can use MultiJSON instead, which will simply choose the fastest available JSON coder. Here's how to use it:

require 'multi_json'

MultiJson.load('{"abc":"def"}') #=> {"abc" => "def"}
MultiJson.load('{"abc":"def"}', :symbolize_keys => true) #=> {:abc => "def"}
MultiJson.dump({:abc => 'def'}) # convert Ruby back to JSON
MultiJson.dump({:abc => 'def'}, :pretty => true) # encoded in a pretty form (if supported by the coder)

The use method, which sets the MultiJson adapter, takes either a symbol or a class (to allow for custom JSON parsers) that responds to both .load and .dump at the class level.

MultiJSON tries to have intelligent defaulting. That is, if you have any of the supported engines already loaded, it will utilize them before attempting to load any. When loading, libraries are ordered by speed. First Oj, then Yajl, then the JSON gem, then JSON pure. If no other JSON library is available, MultiJSON falls back to OkJson, a simple, vendorable JSON parser.

Supported JSON Engines

  • Oj Optimized JSON by Peter Ohler
  • Yajl Yet Another JSON Library by Brian Lopez
  • JSON The default JSON gem with C-extensions (ships with Ruby 1.9)
  • JSON Pure A Ruby variant of the JSON gem
  • NSJSONSerialization Wrapper for Apple's NSJSONSerialization in the Cocoa Framework (MacRuby only)
  • OkJson A simple, vendorable JSON parser


In the spirit of free software, everyone is encouraged to help improve this project.

Here are some ways you can contribute:

  • by using alpha, beta, and prerelease versions
  • by reporting bugs
  • by suggesting new features
  • by writing or editing documentation
  • by writing specifications
  • by writing code (no patch is too small: fix typos, add comments, clean up inconsistent whitespace)
  • by refactoring code
  • by closing issues
  • by reviewing patches

Submitting an Issue

We use the GitHub issue tracker to track bugs and features. Before submitting a bug report or feature request, check to make sure it hasn't already been submitted. When submitting a bug report, please include a Gist that includes a stack trace and any details that may be necessary to reproduce the bug, including your gem version, Ruby version, and operating system. Ideally, a bug report should include a pull request with failing specs.

Submitting a Pull Request

  1. Fork the repository.
  2. Create a topic branch.
  3. Add specs for your unimplemented feature or bug fix.
  4. Run bundle exec rake spec. If your specs pass, return to step 3.
  5. Implement your feature or bug fix.
  6. Run bundle exec rake spec. If your specs fail, return to step 5.
  7. Run open coverage/index.html. If your changes are not completely covered by your tests, return to step 3.
  8. Add, commit, and push your changes.
  9. Submit a pull request.

Supported Ruby Versions

This library aims to support and is tested against the following Ruby implementations:

If something doesn't work on one of these interpreters, it should be considered a bug.

This library may inadvertently work (or seem to work) on other Ruby implementations, however support will only be provided for the versions listed above.

If you would like this library to support another Ruby version, you may volunteer to be a maintainer. Being a maintainer entails making sure all tests run and pass on that implementation. When something breaks on your implementation, you will be personally responsible for providing patches in a timely fashion. If critical issues for a particular implementation exist at the time of a major release, support for that Ruby version may be dropped.


Copyright (c) 2010 Michael Bleigh, Josh Kalderimis, Erik Michaels-Ober, and Intridea, Inc. See LICENSE for details.