Should my store use www or non-www, and where do I set it?

Both addresses work, but search engines prefer one main version. Pick one:

1. Go to Settings → SEO Settings → SEO Settings.
2. Under Preferred Domain (canonical), choose Non-www or www.
3. Click Save Changes.

Visitors who type the other version are then automatically sent (a 301 redirect) to the one you chose, so Google sees one address and no duplicate pages.

Either choice is fine for SEO. Just pick one and keep it. This setting only appears once your store runs on your own custom domain. On a wcart.io address there's nothing to choose.