Helps you to deal with user agents on top of rack.
Switch branches/tags
Nothing to show
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.



Helps you to deal with user agents on top of rack.


gem install uagent_rack


When a browser sends a request to your web application the request has an HTTP_USER_AGENT attribute that identifies the device an browser. For example, the next string identifies an particular model of iPhone, that uses an specific mobile version for Safari.

Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_1_2 like Mac OS X; en-us) 
AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7D11

Each mobile phone model will send you a particular user agent string, thus is a good idea classify the devices in groups an develop a specific interface for each group. For each group we define a key, so the user agent parser receive the user agent string and returns that key. For example, the answer for the string above could be :mobile or :iphone, depending on the parser configuration. To known how to configure the parser read the uagent documentation.

This gem adds the RackParse class to the UAgent module, that extends the Parser class. Unlike Parser, that analyzes the HTTP_USER_AGENT variable every time, uagent_rack parse the user_agent only the first time and store it in the session. Thus, the following requests will be answered using the data in the session. Also, an user can change the user agent adding a value for the parameter user_agent in the URI query.

Code example

require 'rubygmes'
require 'uagent_rack'

parser =

# We create an environment with a mobile user agent.

env1 = {
  "HTTP_USER_AGENT" => "Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_1_2 like Mac OS X; en-us) " +
      "AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7D11 Safari/528.16",
}    # gets :mobile

# We create another that changes the user agent

env2 = {
  "QUERY_STRING" => "user_agent=dektop",
  "REQUEST_URI" => "/index?user_agent=desktop",
})    # gets :dektop    # gets :dektop

Install from code

First you need uagent

$ gem install uagent

Then download the code from the repository:

$ git clone git://

This project uses jeweler to build the gem, so you can use this commands:

$ rake build            # to build the gem
$ rake install          # to build and install the gem in one step

Also, if you want test the gem you can use the spec task:

$ rake spec

This project uses rcov so you can check the coverage opening the HTML file in the coverage directory after running the spec.

Other Stuff


Daniel Hernández,




This software is provided “as is” and without any express or implied warranties, including, without limitation, the implied warranties of merchantability and fitness for a particular purpose.