module ActionController::AllowBrowser::ClassMethods

Specify the browser versions that will be allowed to access all actions (or some, as limited by only: or except:). Only browsers matched in the hash or named set passed to versions: will be blocked if they’re below the versions specified. This means that all other browsers, as well as agents that aren’t reporting a user-agent header, will be allowed access.

A browser that’s blocked will by default be served the file in public/406-unsupported-browser.html with a HTTP status code of “406 Not Acceptable”.

In addition to specifically named browser versions, you can also pass :modern as the set to restrict support to browsers natively supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has. This includes Safari 17.2+, Chrome 120+, Firefox 121+, Opera 106+.

You can use caniuse.com to check for browser versions supporting the features you use.

You can use ActiveSupport::Notifications to subscribe to events of browsers being blocked using the browser_block.action_controller event name.

Examples:

class ApplicationController < ActionController::Base
  # Allow only browsers natively supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has
  allow_browser versions: :modern
end

class ApplicationController < ActionController::Base
  # Allow only browsers natively supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has
  allow_browser versions: :modern, block: :handle_outdated_browser

  private
    def handle_outdated_browser
      render file: Rails.root.join("public/custom-error.html"), status: :not_acceptable
    end
end

class ApplicationController < ActionController::Base
  # All versions of Chrome and Opera will be allowed, but no versions of "internet explorer" (ie). Safari needs to be 16.4+ and Firefox 121+.
  allow_browser versions: { safari: 16.4, firefox: 121, ie: false }
end

class MessagesController < ApplicationController
  # In addition to the browsers blocked by ApplicationController, also block Opera below 104 and Chrome below 119 for the show action.
  allow_browser versions: { opera: 104, chrome: 119 }, only: :show
end