How to test a responsive web design with Firefox
![What the mobile browser mode looks like in Firefox.](https://www.securitronlinux.com/wp-content/uploads/2014/02/mobile.jpg)
If you press Ctrl->Shift->m when viewing a website, it will be switched to a mobile view that allows you to see what the website looks like at various mobile resolutions. I found this out by accident. But this is a very cool Firefox trick. This makes testing a website for mobile customers very easy. The coolest trick in Firefox yet. This will automatically switch a site to the mobile version when you select a mobile device from the list at the top. A great feature for web designers to test a website on the screen sizes of multiple mobile devices. Another way to access this is to navigate to Tools->Web Developer->Responsive Design Mode. A great addition to the Firefox web browser, this is indispensable for testing various website themes on many mobile screen sizes.
![Responsive design mode in Firefox.](https://www.securitronlinux.com/wp-content/uploads/2014/02/Screen-Shot-2018-02-05-at-10.58.04-am.png)
So, you do not need to use many devices to test a responsive website design. Just use Firefox. There is a list of Firefox keyboard shortcuts here, but I could not find this one there: http://www.shortcutworld.com/en/win/Firefox.html. This is very useful for a web designer when wanting to test a new theme or CSS style on many devices screen sizes and resolutions. It is possible to set a different screen resolution on a phone such as a Samsung s20. So this allows this testing as well.