On Twitter, Google’s John Mueller said that you can use your website domain name with or without www. For Google, both versions are the same:
yep— John ☆.o(≧▽≦)o.☆ (@JohnMu) 3. August 2017
Of course, you should focus on one version of the domain. Use redirects and/or the canonical tag to show Google the preferred version of the domain name.
Check if your web pages are listed with both versions
Among many other things, the website audit tool in SEOprofiler checks how many www and non-www pages of your website are linked on your website. It also helps you to correct canonical issues on your pages. If you haven’t done it yet, check your web pages now: