require 'browser'
Browser.modern_rules << -> b { b.ie? && b.version.to_i >= 10 }

Rails.configuration.middleware.use Browser::Middleware do
  redirect_to '/unsupported_browser' unless browser.modern?
end

require 'browser'

Rails.configuration.middleware.use Browser::Middleware do
  supported = !browser.ie? || browser.version.to_i >= 10
  redirect_to '/unsupported_browser' unless supported
end

Adjust unsupported browser rules to be more conservative
Adjust unsupported browser rules to be more conservative

Only block known incompatible browsers: IE 9 and below.
