User Agent information contains identification of the OS, browser, and device type which is sent by computer to the webserver. User agent information is used by the web server to deliver content that matched with system and device used.
User agent strings can be changed / replaced (user-agent spoofing) to fool webserver to delivered content that user want. We do this so we can see the look of the website when opened by other browsers such as Internet Explorer, Opera, Safari or viewed by mobile browser such as Android, iPhone, Nokia, tablet, etc..
Webmaster changed user agent all the time to ensure their website can be opened and read well from a wide range of browsers and devices.
Change User Agent in Chrome
To follow this tutorial you must already have minimum Google Chrome version 17, and install User-Agent Switcher for Chrome plugin.
Once the plugin is installed, a new icon will appear beside the address bar. When you clicked the icon, you can change the browser's user agent (some default user-agent string already provided).
To add a user agent string in chrome, click on Settings (see screenshot above), or go to Tools> Extensions menu, select Options on User-Agent Switcher for Chrome.
An Option page will appear, in the example below I will demonstrate how to insert iPhone 4 user agent string.
User-Agent String: Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_2 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8H7 Safari/6533.18.5
In the Name box type iPhone 4, in User agent string inser the code above, in Append? select Replace, and for indicator flag type ip4 (Note: Name and Flag Indicator can be filled freely). When you're done, click the Add button.
A new option named ip4 will appeared, and when you open a website that have mobile version, Chrome will display that site with same layout & appearance as when opened with the iPhone 4.