Firefox extension User Agent Switcher lets Firefox users change and add new User Agents. I was able to add the iPhone user agent settings using details from TestiPhone.

1) Install User Agent Switcher Firefox extension

2) Add a new User Agent and supply the following information (Tools > User Agent Switcher > Options)

  • Description: iPhone
  • User Agent: Mozilla/5.0 (iPhone; U; CPU like Mac OS X; en)
  • App Name: AppleWebKit/420+ (KHTML, like Gecko)
  • App Version: Version/3.0
  • Platform: Mobile/1A542a Safari/419.3

3) Set the User Agent to your newly created iPhone option

4) Navigate to a website with an iPhone version and enjoy.

Here are some iPhone-compatible places to get you started: