Detect user agent in Rails 4 - read HTTP header

Question

I just switched from PHP to Ruby on Rails and was wondering if there was a way to detect the clients device/user agent (reading the HTTP header) in order to serve different versions of the site depending on the request it gets. In PHP I have been using Mobile Detect to do so. The general idea is to only serve files that are needed for each particular version. Thats why a client side approach is not that effective.

Is there a way to do something similar with Ruby 2.0.0 and Rails 4.0.0 ?

Maybe there is a gem to handle cases like that?

See also http://stackoverflow.com/questions/7650799/is-there-a-way-to-detect-user-agent-in-rails-3-1 — Alistair A. Israel, Oct 23 '13 at 07:39

Paulo Fidalgo · Accepted Answer · 2016-09-16T09:32:55.143

94

Check the request method, where you can get a ActionDispatch::Request where you have all the request parameters, including the user agent.

request.user_agent

edited Sep 16 '16 at 09:32

answered Oct 24 '13 at 08:04

Paulo Fidalgo

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Thanks. I don't see this helpful tip mentioned on either of your two links any more. – MSC Feb 05 '19 at 15:04
The `user_agent` helper is defined in the [`Rack::Request::Helpers` module](https://www.rubydoc.info/gems/rack/Rack/Request/Helpers#user_agent-instance_method) (which is included in `Action::Dispatch::Request`) – Holger Just Jun 07 '23 at 16:32

Detect user agent in Rails 4 - read HTTP header

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