While recently surfing Facebook I noticed a friend had published a link to their new employer’s website. Given this business has over 200+ employees and a large social following I assumed their website was responsive. It was very much not the case.
There’s a free and simple tool Google has for checking if your website is considered mobile friendly:
https://www.google.com/webmasters/tools/mobile-friendly/
Another bonus to having a mobile friendly website is that it’s taken into consideration with search results.