Why is the SEO Moz tool showing that there are duplicates of each page on my site being picked up by Google?

Yes, that can definitely be a problem if you are not redirecting all of your traffic to one or the other. The easiest way to solve this is to add a simple redirect to your site's .htaccess file. Here's an example of how to redirect all non-www traffic to www:

RewriteCond %{HTTP_HOST} ^domain.com
RewriteRule (.*) http://www.domain.com/$1 [R=301,L]

Editing your .htaccess file can be a little tricky, so be sure to do a little platform-specific research first before you do this as you could easily break your site!

Yep, this is quite common. Eventually Google will figure out that the two versions are one and the same, but it's a good idea to implement a site-wide redirect from one version (with or without the www) to the version you want.

There are simple ways to do this depending on what type of server your site is on. Talk to a developer or your web host about this.

If it's showing those duplicates AND your website does in fact show up for both URLs without redirecting, then yes that's something I've come across before and that's something for you to fix.

Each page on your site should show up for the www or non-www but not both. Choose whichever one has the most Domain Authority (Moz metric) and redirect the other version to that. Your developer should know how to do so. WWW is often recommended the most.

Paste "site:example.com" (replace example with your name) into Google search to see what version of your URLs is indexing the most.

It's a weird technical thing, but it's worth making sure you have it done right. It's most likely not going to be a game changer, but it will help your site to a small percentage to have that properly in place.

Happy to answer any other questions on this!

This is a very common problem and can be described as being an issue with 'canonicalisation'. Essentially, you only want to show one (or canonical) version of your web content to search bots as opposed to multiple versions across varieties of URLs e.g. www.domain.com, domain.com, https://domain.com etc.

This problem can be solved in a selection of ways:

Canonical tag - use the canonical link element referencing the preferred URL.

Permanent redirects - use a 301 redirect to the preferred URL.

Set your preferred domain in Google Search Console - this is the easiest, due to the lack of dev time required and seems to suit your specific issue.