Chai is available for both node.js and the browser using any test framework you like. There are also a number of other tools that include Chai.


Package is available through npm:

npm install chai

Recommend adding it to package.json devDependencies using a * as the version tag. This will ensure that you always have the most recent version after running npm install, which can be especially powerful when paired with a continuous integration tool.

"devDependencies": {
  "chai": "*",
  "mocha": "*"
}, "//": "mocha is our preference, but you can use any test runner you like"


Include the chai browser build in your testing suite.

<script src="chai.js" type="text/javascript"></script>

This will provide chai as a global object, or define it if you are using AMD.

The latest tagged version will be available for hot-linking at http://chaijs.com/chai.js. If you prefer to host yourself, use the chai.js file from the root of the github project. We recommend that you always use a version tag as your starting point, so the tag download list is the best place to start.

Currently supports all modern browsers: IE 9+, Chrome 7+, FireFox 4+, Safari 5+. Please note that the should style is currently not compatible with IE9.

If you want to know if your browser is compatible, run the online test suite.

Other Platforms



For testing your Ruby on Rails application using Chai assertions and the Mocha test framework, check out Konacha – a modern test harness that takes full advantage of Rails 3 features such as the asset pipeline and engines.

© 2017 Chai.js Assertion Library
Licensed under the MIT License.