How to Quickly Switch User Agent String in Firefox

When you open a website in your web browser, you download the content from the web server hosting that website, but your browser also sends some data to the web server. Among other things, the web browser sends a text string called the user agent string that describes the web browser and the operating system you are using to access the website. This information is then used by the website to deliver the browser specific or the platform (operating system) specific content. You can modify this user agent string to view a version of website meant for other operating systems or web browsers. The newer versions of the Firefox web browser make it very easy to switch the user agent string without using any extensions.

You can follow these simple steps to switch the user agent string in Mozilla Firefox:

  1. Press the hotkey Ctrl+Shit+M to open the web developer’s responsive design mode. Alternatively, you can also select Tools → Web Developer → Responsive Designs View from the menuabar.
  2. In the responsive design view, you will find a specific text box to enter the user agent string. You can find the user agent strings for various browsers and bots on the web site and copy/paste them into this text box.User Agent String in Firefox
  3. You can change the resolution of the frame inside the responsive designs view to make it fit the entire screen of your PC and keep browsing any website you want using the altered user agent string. You can check the changes to your user agent string by visiting the website
  4. Press the same hotkey (Ctrl+Shit+M) once again to close the responsive designs view mode when you are done browsing. This will also remove the user agent string from the browser.

This way you can switch the user agent strings to anything you want in the Mozilla Firefox web browser without having to install any extensions at all.