ohler55/oj

---

ohler55/oj.json

{
  "createdAt": "2012-02-17T09:30:32Z",
  "defaultBranch": "develop",
  "description": "Optimized JSON",
  "fullName": "ohler55/oj",
  "homepage": "http://www.ohler.com/oj",
  "language": "C",
  "name": "oj",
  "pushedAt": "2025-11-25T05:09:58Z",
  "stargazersCount": 3183,
  "topics": [
    "c",
    "json",
    "json-parser",
    "marshaller",
    "oj-gem",
    "rails",
    "ruby",
    "ruby-json-parser"
  ],
  "updatedAt": "2025-11-25T05:10:02Z",
  "url": "https://github.com/ohler55/oj"
}

gem

A fast JSON parser and Object marshaller as a Ruby gem.

Version 3.13 is out with a much faster parser (Oj::Parser) and option isolation.

Using

require 'oj'

h = { 'one' => 1, 'array' => [ true, false ] }
json = Oj.dump(h)

# json =
# {
#   "one":1,
#   "array":[
#     true,
#     false
#   ]
# }

h2 = Oj.load(json)
puts "Same? #{h == h2}"
# true

Installation

gem install oj

or in Bundler:

gem 'oj'

Rails and json quickstart

See the Quickstart sections of the [Rails]!(pages/Rails.md) and [json]!(pages/JsonGem.md) docs.

multi_json

Code which uses multi_json will automatically prefer Oj if it is installed.

Support

Get supported Oj with a Tidelift Subscription. Security updates are supported.

Further Reading

For more details on options, modes, advanced features, and more follow these links.

• [{file:Options.md}]!(pages/Options.md) for parse and dump options.
• [{file:Modes.md}]!(pages/Modes.md) for details on modes for strict JSON compliance, mimicking the JSON gem, and mimicking Rails and ActiveSupport behavior.
• [{file:JsonGem.md}]!(pages/JsonGem.md) includes more details on json gem compatibility and use.
• [{file:Rails.md}]!(pages/Rails.md) includes more details on Rails and ActiveSupport compatibility and use.
• [{file:Custom.md}]!(pages/Custom.md) includes more details on Custom mode.
• [{file:Encoding.md}]!(pages/Encoding.md) describes the :object encoding format.
• [{file:Compatibility.md}]!(pages/Compatibility.md) lists current compatibility with Rubys and Rails.
• [{file:Advanced.md}]!(pages/Advanced.md) for fast parser and marshalling features.
• [{file:Security.md}]!(pages/Security.md) for security considerations.
• [{file:InstallOptions.md}]!(pages/InstallOptions.md) for install option.

Releases

See [{file:CHANGELOG.md}]!(CHANGELOG.md) and [{file:RELEASE_NOTES.md}]!(RELEASE_NOTES.md)

Links

• Documentation: http://www.ohler.com/oj/doc, http://rubydoc.info/gems/oj

• GitHub repo: https://github.com/ohler55/oj

• RubyGems repo: https://rubygems.org/gems/oj

Follow @peterohler on Twitter for announcements and news about the Oj gem.

Performance Comparisons

• Oj Strict Mode Performance compares Oj strict mode parser performance to other JSON parsers.

• Oj Compat Mode Performance compares Oj compat mode parser performance to other JSON parsers.

• Oj Object Mode Performance compares Oj object mode parser performance to other marshallers.

• Oj Callback Performance compares Oj callback parser performance to other JSON parsers.

Links of Interest

• Fast XML parser and marshaller on RubyGems: https://rubygems.org/gems/ox

• Fast XML parser and marshaller on GitHub: https://github.com/ohler55/ox

• Need for Speed for an overview of how Oj::Doc was designed.

• OjC, a C JSON parser: https://www.ohler.com/ojc also at https://github.com/ohler55/ojc

• Agoo, a high performance Ruby web server supporting GraphQL on GitHub: https://github.com/ohler55/agoo

• Agoo-C, a high performance C web server supporting GraphQL on GitHub: https://github.com/ohler55/agoo-c

• oj-introspect, an example of creating an Oj parser extension in C: https://github.com/meinac/oj-introspect

Contributing

• Provide a Pull Request off the develop branch.
• Report a bug
• Suggest an idea
• Code is now formatted with the clang-format tool with the configuration file in the root of the repo.