In the earliest days of the internet, it was assumed that all visitors to a website would be using one of just a handful of different browsers running on a desktop computer. Today, visitors use a wide array of different devices to access a website, including tablets, mobile phones, smart objects, and desktop computers.
Instead of having to create different theme designs for each browsing device, WordPress now recommends using responsive themes. As you might expect, the term “responsive” refers to the fact that the theme responds to the visitor’s browsing device to dynamically optimize how content is displayed.
Furthermore, Google and other leading search engines now recommend that all websites have fully responsive designs. A few years ago, you could get away with having different versions of your website for desktop computers and mobile browsers, but this is no longer the case.
Most WordPress themes are now classified as responsive, but you may have to activate this feature. From your administration panel, click on “Appearance” in the left-hand column and then “Mobile.” From here, you’ll be able to decide whether to enable a mobile theme and make other adjustments to how the content on your website is displayed to mobile browsers.
Furthermore, when you preview your website, you’ll be able to see how your content is displayed based on three standardized views: a full-screen one for a desktop computer, a smaller one for tablets, and the smallest one for mobile phones.
If your website is publicly accessible (i.e. not set to private), then you definitely want to make sure that you are using a responsive theme. There are thousands of responsive themes available at WordPress.org and from third-party websites. Before installing a new theme, make sure that it is labeled as responsive.
Note: Some themes have the word “Responsive” in their title, but this is just the title. What matters is that the theme description includes the word “responsive.”