It Does Not Matter Which One You Pick
www or non-www. Either is fine for SEO. Google has said this explicitly.
What matters is that you pick one and redirect the other.
The Problem When You Do Not
If both `www.example.com` and `example.com` serve your site without redirects, you have duplicate content across your entire domain. Every page exists at two URLs. Link equity is split.
The Fix
Choose one version. Set up a 301 redirect from the other version. Update your canonical tags, sitemap, and internal links to use the chosen version. Google's SEO starter guide confirms both are equally valid.
Most sites use non-www these days. It is shorter and cleaner. But www is fine too.
Just. Pick. One.
Check it off at seocheckup.app. 113 tasks. Free. No credit card.