Facebook lists a person's groups on their profile under Groups, but the list respects two things at once: the person's own audience setting for the section, and each group's privacy. A public group appears to anyone who can see the section. A private group appears only to its members, and a hidden group appears to nobody outside it.
Paste the profile link and press the button. Groups under Profile opens the visible list. From there each group links to its own page with the member count, the description and, for public groups, the posts.
Many of these groups are for buying and selling. To check a seller before you meet, the Marketplace profile page opens what they sell and their ratings.
Public, private and hidden
Public: anyone can see the group, its members and its posts.
Private and visible: anyone can find the group and see who is in it, but only members see posts.
Private and hidden: only members can find the group at all.
Buy-and-sell groups, local groups and school groups are nearly always public, which is why they show up most often. Support and hobby groups tend to be private.
What groups tell you
The city groups place a person. The school and alumni groups date them. The buy-and-sell groups show what they are shopping for. And group posts are the one place where people write at length in public, so a public group's search box with the person's name in it is often the richest source on the whole profile.
Common questions
Does this show secret groups?
No. Secret and private groups do not appear anywhere in Facebook search, so they cannot appear here either.
Do I need an account on StalkFace?
No. You paste a profile link and get search links back. You open them in your own Facebook session, in the same browser.
Does Facebook tell the person?
No. StalkFace never touches their account. It builds a search link, and Facebook does not notify anyone about searches or profile views.
Can I see posts someone made in a private group?
Only if you are a member of that group. Facebook shows private group posts to members and nobody else.
Why does the group list look shorter than I expected?
Hidden groups and private groups you are not in are left out, and the person may have set the Groups section to Friends only.
Can I see a private Facebook group without joining?
Only from the outside. Anyone can see a private group's name, description, member count and rules. Posts and photos open only for members, and someone in the group has to approve your request to join. A hidden group does not show up at all unless you are a member or invited.