The obvious answer might seem to be: Whip out your phone and take a look – but that might not show you everything.
Do I have a mobile version?
Does your website just show the regular desktop layout on a mobile? This is going to make your site hard to read, buttons very hard to click and users will have to zoom in and out as they scroll around your website to try to see everything.
Does your website have a responsive layout or a mobile only version? While a completely separate version of the site on a different URL such as m.yoursite.com is ok we recommend having a flexible responsive site layout that loads on the same URL (and have done so since before responsive layouts won out in popularity).
Browsers vs Search Engines
Search engines may not see your site the same way your users do so we can check this also.
What does Google think?: https://search.google.com/test/mobile-friendly
Site Load Speed
Mobile websites are often viewed from a (slower than WiFi) 3G mobile network and connectivity speeds could make your site load even slower than normal.
How fast does the mobile version of your site load?: https://testmysite.thinkwithgoogle.com/
You can also try PageSpeed Insights: https://developers.google.com/speed/pagespeed/insights/
After these basic checks you should look at a site-wide mobile usability report.
You will need Google Search Console setup for the website: https://www.google.com/webmasters/tools/mobile-usability
Your site is also going to be shown slightly different depending on the device, screen size and browser.
BrowserStack (paid service) has a great tool that can show you how your site looks on various devices: https://www.browserstack.com/responsive
How important is it?
Having a mobile-friendly website is no longer optional. Smartphone traffic now exceeds desktop traffic in most parts of the world. This means that a lack of a mobile friendly website could be costing more than half your potential website traffic.
Intaprise only makes mobile responsive websites so if you are looking to upgrade your current online presence, take a look at our website options.