The modernizr-rails gem will include the Modernizr.js library (https://github.com/Modernizr/Modernizr) into your Rails 3.1 or higher app via the asset pipeline. This modernizr.js file was built using the builder located at http://www.modernizr.com/download/ with all options checked.
How to Use
Add the following to your Gemfile:
Then add the following to your application.js manifest:
//= require modernizr
Or to use the minified version:
//= require modernizr.min
Don't forget to run
bundle update after upgrading to the latest gem version to ensure it's used by your rails app.