Mobile-Friendly Test is handy tool created by Google which will scan any URL and tell you firstly whether or not the page is mobile friendly and secondly, if it isn't, what you need to improve to make it so. As Google is now using mobile friendliness as a search ranking factor, it's wise to ensure that this tool considers your site to be mobile friendly.
It's as simple as heading over to this page and entering your website's URL. Bear in mind that the test is only analysing that specific page, not your entire website, so you may want to check multiple different pages for potential issues.
Once the test runs, you'll hopefully see a nice friendly green message telling you that there are no problems - if you do, you can close the window and move on with your life. If not, however, then you've got some fixing to do! Read on for an explanation of some of the most common issues new developers run into.
I've put this first as, while it's probably not that common an issue, if your site is otherwise coded well then adding a viewport declaration could fix a number of errors. To resolve this issue, simply declare the viewport in your website's
<head> with the following snippet:
<meta name="viewport" content="width=device-width, initial-scale=1">
This could be a caused by a multitude of different things, but to resolve it you want to ensure that on mobile devices all of your content is stacking into neat, block level elements.
Fingers are surprisingly big and clumsy when it comes to interacting with a small touch screen. If you have 2 tiny little links right next to each other, it's going to be hard for the user to consistently select the right one. On mobile devices you must ensure that your links are big, chunky and well spaced.
It's hard to put a hard limit on it, but on some devices any text which is under 16px is going to be difficult to read, and much smaller than that will make it impossible. Bump those font sizes up on mobile!
Hopefully this article has helped you get up to speed with Google's Mobile-Friendly Test. It's extremely important that you pass this test if you want to ensure a fair fight in the search engine, but the good news is if you're building solid, responsive websites you'll find most of your websites are a pass anyway, or will only require a couple of small tweaks.