TL;DR: People You May Know (PYMK) uses mutual friends, shared workplaces, schools and groups, and the contact lists people upload. That last one is why Facebook can suggest someone you only ever phoned: if they saved your number, Facebook can connect you. You can't switch PYMK off, but you can stop uploading your contacts, delete ones already uploaded, limit who can find you by phone or email, and remove suggestions.
Where the suggestions come from
Facebook's help centre lists the main signals: mutual friends, work and education information, networks you're part of, groups, and contacts you or others have uploaded. Most suggestions are obvious. The odd ones usually come from contact uploads.
Why it suggests people you barely know
When someone lets Facebook or Messenger upload their phone contacts, your number and email go with them, whether or not you use Facebook. Reporting by Kashmir Hill for Gizmodo in 2017 showed how this created surprising links: a social worker's client suggested to her, an attorney shown opposing counsel, people who had shared nothing but a phone number. Facebook said at the time that suggestions “may be based on contact information we receive from people and their friends.”
This is also why Facebook may know your number even if you never gave it, which is the idea behind a “shadow profile.” Our explainer on Meta's Download Your Data shows what you can see of your own file.
How to reduce PYMK suggestions
Stop uploading your contacts
Per Techlicious' walkthrough: in the Facebook app go to Settings & Privacy, Settings, Media & Contacts (or similar), and turn off Upload Contacts. In Messenger, turn off Upload Contacts in People settings. Do it on every phone you use, or they'll upload again.
Delete contacts already uploaded
Find “Your Address Books” under your Facebook information (the menu sits inside Accounts Center in newer versions) and delete all.
Limit lookups by phone and email
Under How People Find and Contact You, set who can look you up using your email address and phone number to Only me or Friends. It won't stop other people's uploads, but it removes one signal.
Remove or hide suggestions
Tap Remove on any suggestion you don't want, and use the option to hide PYMK from your feed if it's shown there.
When suggestions are a safety issue
If Facebook keeps suggesting an ex or someone you've cut off, block them: blocking stops you appearing to each other. If you're worried someone is tracking you, see our guides on your digital footprint after a breakup and signs of stalkerware on your phone.
Lock down the rest of your profile with how to make Facebook private.
Your phone number links you across apps. A free email exposure check shows whether your email is in known breaches, and the full Scan My Shadow scan adds your phone number.
Frequently Asked Questions
How does Facebook know who to suggest in People You May Know?
It uses mutual friends, shared work and education info, networks, groups and contact lists that you or others uploaded.
Why does Facebook suggest people I’ve only called or texted?
If either of you uploaded phone contacts to Facebook or Messenger, Facebook can connect the two accounts through the shared number.
Can I turn off People You May Know?
Not completely. You can stop contact uploads, delete uploaded contacts, limit lookups by phone and email, and remove or hide suggestions.
Does Facebook tell people I viewed their profile?
No. Viewing a profile doesn’t notify anyone, and Facebook does not offer a list of profile viewers.
How do I stop someone appearing in my suggestions?
Remove the suggestion, or block the person, which stops you appearing to each other.
Sources
- Facebook Help: Where People You May Know suggestions come from
- Gizmodo: How Facebook figures out everyone you’ve ever met (Nov 2017)
- Techlicious: Delete contacts you uploaded to Facebook