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Lots of Ruby libraries utilize JSON parsing in some form, and everyone has their favorite JSON library. In order to best support multiple JSON parsers and libraries, multi_json is a general-purpose swappable JSON backend library. You use it like so:

require 'multi_json'

MultiJson.engine = :yajl
MultiJson.decode('{"abc":"def"}') # decoded using Yajl

MultiJson.engine = :json_gem
MultiJson.engine = MultiJson::Engines::JsonGem # equivalent to previous line
MultiJson.encode({:abc => 'def'}) # encoded using the JSON gem

The engine setter takes either a symbol or a class (to allow for custom JSON parsers) that responds to both .decode and .encode 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 Yajl-Ruby, then the JSON gem, then JSON pure. If no JSON library is available, MultiJSON falls back to a bundled version of OkJson.

Continuous Integration

Build Status


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. You can indicate support for an existing issuse by voting it up. 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 project.
  2. Create a topic branch.
  3. Implement your feature or bug fix.
  4. Add specs for your feature or bug fix.
  5. Run bundle exec rake spec. If your changes are not 100% covered, go back to step 4.
  6. Commit and push your changes.
  7. Submit a pull request. Please do not include changes to the gemspec, version, or history file. (If you want to create your own version for some reason, please do so in a separate commit.)


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

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