Duplicate content often creeps in without anyone deciding to publish it, through printer-friendly pages, parameter variations, or inconsistent www settings.
Check Your www and Non-www Versions
Confirm both versions of your domain consistently redirect to a single preferred version rather than both being independently accessible.
Look for CMS-Generated Duplicate Pages
Tag archives, category pages, and auto-generated print versions are common, often-overlooked sources of near-duplicate content.
Consolidate What You Find
Once identified, duplicate pages should be redirected or canonicalized to a single preferred version rather than left competing with each other.
Next step: Use the SEO Audit to check your site for duplicate content issues you might not have noticed yet.