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Where Do Facebook Friend Suggestions Come From?

Question: I have occasionally received ‘invitations’ from people, most of whom I know only vaguely, to join them on Facebook. I’ve no wish to join Facebook, so just ignore these. Yesterday, however, I received yet another invitation, from someone who runs art classes I once enquired about. Underneath, Facebook lists three other people who have invited me in the past. And, below that, there is a list of nine other people ‘whom you may know’ – none of whom have ever invited me, and three of whom I have had only very basic contact with – eg a single enquiry made to an archivist.

This really worries me – how does Facebook know that I have ever had any contact with these people? Can Facebook access their emails, see where they are all going to, and cross-reference them with people who have received an invitation from elsewhere? Or can they, having once been given my email address, somehow gain access to my Sent messages, see where they are being sent to, and cross-reference them against their existing Facebook membership??

This really worries me – it just seems such an invasion of my privacy, and concerns me that they may be able to access all sorts of personal information and conversations.

Can you explain how this can be happening, and suggest any way to block it, please??

I’m not privy to all the details of how Facebook works. That being said, I can hazard a guess as to how Facebook (or any social network with similar capabilities) might be making these recommendations.

No, Facebook is not looking at anyone’s email (outside of messages sent on Facebook itself).

Facebook friend suggestions and invitations to join Facebook — whether emailed, or suggestions when signed in to Facebook — are nothing more than what I’d characterize as very educated guesses.

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Tom and Dick, meet Harry

Here’s one way I think this happens:

  • Your friend “Tom” sends you a friend request, which you ignore. However, Facebook remembers that he did so.
  • Another friend, “Dick”, also sends you a friend request, which you also ignore. Once again, Facebook remembers.
  • “Tom” and “Dick” have a friend in common — I’ll call him “Harry”. Both Tom and Dick invited Harry to be friends, and Harry accepted.

Be My Friend? So, here’s what Facebook knows:

  • Tom claims to know you.
  • Dick claims to know you.
  • Tom and Dick both know Harry.

The educated guess is: since Tom and Dick both claim to know you and Harry, perhaps you know Harry. Hence, Harry becomes an “other person you might know”.

And you might. Or you might not.

Mutual interests

Another scenario plays out based not on mutual friends, but mutual interests.

  • As before, your friend “Tom” sends you a friend request, which you ignore and Facebook remembers.
  • “Dick” also sends you a friend request, which you also ignore and Facebook remembers.
  • “Tom” and “Dick” both happen to have “Liked” a page on Corgis.

So, here’s what Facebook knows:

  • Tom claims to know you.
  • Dick claims to know you.
  • Tom and Dick both like a Corgi page.

A different educated guess is that since Tom and Dick both know you, and they share a liking of Corgis, you might also like Corgis. In fact, you might like to be friends with other people who also liked the Corgi page. So Facebook picks someone at random who also likes the Corgi page and suggests that you might like to be friends.

Of course, if there’s more overlap — more mutual interests Facebook knows about — it might pick people who have the most in common with Tom and Dick, and thus hopefully you.

If you are already on Facebook

This kind of shared-connections-and-interests analysis goes on in significantly more detail if you already have a Facebook account. Facebook then can throw into the calculation the pages you liked, the friends you accepted, the posts you clicked on, liked, and shared, and even your location and other data you’ve given it.

The result is that they might suggest complete strangers as possible friends.

I find about 50% of Facebook’s initial recommendations are people I don’t know, and about half of the remainder are people I might know but don’t want to connect with anyway.

It’s not something I worry about

Now, as I said, I don’t know exactly how Facebook — or any social network — actually works. In fact, I’d be willing to bet that the details are significantly more complex. If nothing else, they are privy to millions of relationship connections, interests, and actions to make these inferences.

But I’m willing to bet it’s just that: nothing more than Facebook analyzing all the data its members have provided to infer who might know who — even for people who are not yet members.

I get that it might seem a little creepy, but I don’t believe it’s as intrusive as you fear. It’s simply using the social relationships its members provide to make a few well-educated guesses.

Unfortunately, to answer your last question, I’m not aware of a way to actually block Facebook’s emailed invitations, other than to perhaps report them as spam.

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34 comments on “Where Do Facebook Friend Suggestions Come From?”

  1. One friend recommendation that had me wondering about for a long time was a real estate agent I only met with once. The only idea that comes to me as to how that happened is that she may have uploaded her email contacts list.

  2. I’ve always assumed a simpler answer. Facebook asks if its members want to upload their email address book(s, so it can suggest new friends. If Tom, Dick or Harry have (or had) your email address, and uploaded their address book, then Facebook KNOWS that they know you, and can infer that you know them, so suggests them as friends for you.

  3. There will be words in common in the subject lines of these kinds of emails. EG: “facebook”. Use the filter system on your email package to send them straight to your Trash folder.

  4. I pieced this scenario together myself:

    FB, with your permission, can search your email contacts. You may not have given them permission to search your contacts, but someone else with your email address may have.

    So, if someone you have ever sent a message to saved your email address in their contacts, and it’s the email address that you use on FB, and that someone gave FB permission to search through their contacts, then they will be presented as someone you may know because FB (apparently) saves that info.

    I’d say their database schema is impressive in many ways, with the breadth and wealth of data mined and to be mined being first and foremost.

  5. I agree with the scenario suggested by David Powell and Michelle above. I once had a Facebook suggestion that I friend someone whom I do know, but who I don’t think knows any of my Facebook friends. I have never given Facebook permission to search through my e-mail address-book for other Facebookers I know.

    I am relieved to read that people think that these random suggestions from Facebook come from other people one has been in contact with giving Facebook permission to search their contacts, and not from Facebook looking through my e-mails without permission; at the time I couldn’t think of another way in which this might have happened, and was offended!

  6. I tried FB for about 6 months and then got tired of all the useless information being sent back and forth. Some people seem to have a lot of time to talk about what they eating, doing, reading, watching etc….boring [edited]. I love my friends but I’d rather have a meaningful conversation via email or phone.

    • I totally agree with you about the talking about what they are eating etc.

      I’ve never been a fan of (anti)social media. At. All. I was totally sceptical way back in the Bebo and MySpace days. Could see ALL the negatives and virtually no positives.

      Hence the reason I refer to it as either Fakebook or Farcebook. Depends which side of the bed I wake up on.

  7. A good question. I often ask myself the same question. The only answer I can come up with is that someone is looking up all names and thinks he or she recognises a name and place and invites tha person to be a ‘friend’ on Facebook What they don’t consider is that two or more people living in the same can have the same name. Facebook somehow remembers these names and comes with the same suggestion. It very often frustrates me so much that I wish I could unsubscribe to Facebook like we can with ‘Buzz’

  8. I recently took a course (Facebook Essentials)on (no relation-it’s a popular educational site for online courses) which was very thorough about how Facebook works. It may be helpful to this reader. They don’t have the type of info Leo offers (no competition there, Leo! You’re in a class by yourself-a great resource! I love your newsletter); they teach mostly software programs. I had a free month coupon, but it only costs $25 a month for access to all their courses. Anyway, it really helped me learn how Facebook works – and the teacher is open to receiving contact following the course. Best of luck!

    While I’ve not used it myself, I’ve also heard fairly good things about


  9. Leo

    I had a friends very personal photos accidentally show up in my Facebook once.

    Just like spam and viruses have their issues and we need to protect ourselves, social networking sites have their issues.

    These sites are in business to make a profit, your personal information is what makes it profitable.

    Joining these sites is a trade off of personal information against what we value we get from joining.

    Here are my basic assumptions that I use to protect my privacy:

    1- Anything you pass through or post on those sites, now belong to the site.

    2-You may loose copyright privileges to your photos. You may loose copyright privileges to your written material.

    3- Also assume that there is a clause in the User Agreement that lets them mine your contacts from other sites or wherever.

    4- The terms of the agreement are always subject to change without notice. If a concept sounds unethical today, they still may get away with it tomorrow after you join. Protect Your Privacy.

    I now see websites trying to get you to upload your photo for various reasons, one is to make a cartoon of yourself. This is blatant data mining with new face recognition software and should be illegal for them to troll for minors.

    Here’s part of Leos Terms of Service for posting here:
    By posting a comment you grant Puget Sound Software LLC, Ask Leo! and Leo A. Notenboom the unrestricted right to publish or reuse that comment in other forms, including but not limited to other publications and web sites.

    • The permission to Puget Sound Software, etc., is necessary because of copyright: without such permissions, PSS couldn’t post your comment without violating your copyright!

      I think you’ll find similar language to be a standard boilerplate on any site that posts user-submitted commentary.

      • I’m not convinced that’s actually required (as always, I’m not a lawyer), but it’s certainly easier, better, clearer to include that verbiage just to be safe.

  10. I am now getting e-mails that purport to be from Face book. (I’m not a member) These messages tell me my password has been ghanged for security reasons. They have a place to click on to see my new password. Clicking will install a virus PAKES.EQR. I am not inferring that Face book is sending this message.

    • I got hacked somehow, changed password twice (FB) still get scam messages from people I know. Thinking about dumping FB but sadly there are some benefits (search for old friends) that make it valuable. If the fake messages from “friends” do not stop though will bail.

      • That isn’t usually a sign of your account being hacked.
        Scam messages from people you know often come because those people took a quiz or played a game and posted the results on Facebook. Those usually ask your permission to access your friends list and then send spam posts to people on that list.

  11. i started to join face book and gave preliminary information–name, age, email address but balked when they asked me for my email password. was this site legit? i don’t know. they also had 2 suggested friends that i knew and whose names and addresses are in my email address book. so i suspect they are somehow mining address books.

  12. 1. Facebook is done by gigantic robotic machines processing bazillions of ones & zeros, using various formulae – or so-called ‘algorithms’; i.e. it’s not done by humans reading emails, or nefariously accessing databanks, or whatever. The end result is uncomfortable, nevertheless.
    2. Leo’s Tom+Dick+Harry example is at it’s core – PLUS the cross-referencing of email addresses, correlating photo tags, personal information made available to applications (including 3rd-party ones), clicking on ads, making enquiries on those ads, how regularly this is done, I.P. numbers – which give the country & approximate location of the user, & similar activity by users on their friends pages, groups etc, etc. Another user, with whom you have no contact, may be in the address book of yet another user who you once made an enquiry from – about, say, art classes! Ever notice the way users are encouraged to sync their Hotmail address books with Facebook? So, you have a friend, or even someone you hardly know, who has a 16 year old son & daughter who just happen to also have you in their address books – which they’ve synced with their Facebook accounts! And there’s much, much more. A continuous & endless correlation of links, which are the basis of the internet itself. Put malware & hacking into the mix, and even those programs on your PC that connect to the web, unnecessarily and without your knowledge, and, well, enough said.
    3. The complexity is mind-boggling, and the above is only part of it. The web as we know it would not be the same without it. And of course it does have very dark side. It’s all benefit vs. risk, and vice-versa. No matter what is put on the web is there, and it’s there forever. Electro-magnetic ones & zeros containing that love letter I emailed 15 years ago. Aaaaagh!!!!

  13. I had just signed up for Facebook, and I did not allow it to check my email contacts, or anything else. Nor did I give it any personal information other than my name and age. Not my schools, nothing else. The next day, I looked at Classmates at a listing of an old classmate I hadn’t thought of for 40 years. I looked up her page on Facebook, but didn’t contact her or anything. Two days later, she sent me a friend request. This is someone I was never even really friends with, and hadn’t seen or talked to since 6th grade. Facebook had to have given her my name as a suggestion.

    As outlined in the article: perhaps via a mutual friend on Facebook or other simple relationship that’s visible there.


  14. When one goes to Facebook, the option for them to check your email address book comes up. If you allow Facebook to do that, then every single entry in your address book is listed as 1. a member or 2. a potential member. This includes email addresses such as

    I allowed Facebook to look up people in my address book ~ but I have no idea who half these people are ~ but that is one way the list is generated.

  15. Folks, if you are so worried about privacy, don’t peek your head out the door, and do away with your real world mail box! If you go outside, your neighbor will see you. If you get mail, junk mail will come to your mail box, some of it (GASP!) with your name on it. None of this is an invasion of your privacy, and it is the same with Facebook. You surf the web, use email, and you will be known by people. The only way to get your privacy infringed is to get software on your computer that steals it. Facebook can’t do that.

  16. @ Sharon: Facebook has a 3rd party application callied “Friend Facts” that contains rude questions. It is automatically generated, not actual postings. I’ve seen the same dozen or so questions asked about more than 30 people.

    This application can be blocked by going to the account drop-down menu, and hitting the application settings button. A list of apps you use will come up. Find “Friend facts” and press the small x on the right and confirm to permanently block. This will work on any app you don’t want.

  17. One thought of mine about facebook friend suggestions is that as soon as one joins or becomes a fan of a group, other fans are suggested to you as friends. If the “fan club” is small, one can compare notes and see it matches the people there. I presume Facebook reasons _birds of a feather, flock together_ :)

  18. How do you find out who gave the friend suggestion on facebook? Someone suggest someone they know i would not add.

    I don’t beleive you can.


  19. I recently joined facebook and the first suggestion as a friend was a woman who I had a brief relationship 10 years ago. I have had no contact with her since then and I had no idea where she was. Her surname has changed so I assume she has got married.

    Given that we have had no contact of any kind for all this time, she doesn’t appear in my address book I found it bizarre that this name should suddenly appear. It’s definitely the same woman.

    I have resisted the temptation to make contact let alone to add her as a friend but how on earth have they made the link. I have checked her profile and she has 3 friends none of whom I’ve ever heard of.

  20. How Friend Finder works

    We will not store your password after we import your friends’ information.

    We may use the email addresses you upload through this importer to help you connect with friends, including using this information to generate suggestions for you and your contacts on Facebook. If you don’t want us to store this information, visit this page.

  21. This is another educated guess. Facebook has a search for Facebook friends via your email address book. You logon to your web mail or connect it to your email client address book and it searches for Facebook members with that email and gives you the option of inviting them. If their email addresses aren’t associated with a Facebook account, FB then offers to send an email to them an email invite. So it’s possible some of your contacts from years ago may send you an FB invite with that option. FB then may or may not store this info for further invitations.

  22. This is the scary part: When you have an excisting facebook account from your pc where you normally login to your facebook account, make a new emailadres. Make a new facebook account with this new email addres. After some time you get a friendsuggestion from the new facebook account (and vice versa). No emails/no contact sent to standard and this new emailadress.

    • I have a similar situation and it IS spooky. I set up a facebook account with my main email address MANY years ago, and have accepted some friends and family members when they contact me. I don’t seek them out. I did not put in my date of birth or high school or town, etc. I do not post about myself often, but I do look at friends pictures and posts, usually when facebook sends me an email.

      About 3 or 4 years ago, I wanted a pen-name facebook account specifically for making comments on a radio show related page. So I created a new email address and a new facebook account for my pen-name. I do not use the email address for anything else. It is not top secret, but I don’t want my real name read out on the radio.

      At first the facebook account got friend suggestions for complete strangers, usually with African sounding names. Then in the past six months, some of the friend suggestions were other people who comment on the radio show page – fair enough, we have a common interest. But this week, I have suggestions of real friends and family on my side and my husband’s side. My family is in another continent – I don’t think they have HEARD of the radio station, let alone the radio show!

      I have used both these accounts on the same computer at home and at work. I don’t log out every time, though, maybe that is the problem? I guess I’ll never know – betting facebook won’t tell me!!

  23. I also have freind “suggestions” from Facebook as peoplei may know. I believe these may be coming from my phone address book, linking it to the phone numbers supplied on the person Facebook page. I have some of these from people who have no connection to me whatsoever except that through business they are in my contacts. If its not this, is it possible they have searched me or mentioned me? I have certainly never mentioned or searched them.

  24. I have found that every time I search for someone on facebook, or browse a page of a friend of a friend, those persons turn up in my friend suggestions within days, sometimes even hours. I have gone into my search history and cleared my searches, but, not only does this still happen, the search box “remembers” the names of people I have searched and presents them in a drop down list as I type. This becomes very annoying when you try to narrow it down to the one person you are searching for, and all others with similar names turn up on your friend suggestions. I find the whole friend suggestion mechanism extremely irritating and intrusive.

    • Easy: Go to the menu (upper right beef burger; same as the one that contains ‘Log Out’).
      – Settings & Privacy
      – Settings
      – Personal information
      – Manage account
      – Account -> Deactivate
      I have not tried it. It may work.

  25. I stopped going on FB a few months ago. For the past month I have had numerous “friend suggestions” pop up on my laptop while I am browsing the internet. Here’s what I think is happening and I’m almost positive I am right. Even though I have intentionally never downloaded the FB app on my phone, I believe they have gotten into my contacts(cellphone #’s and email)! So far I have had my plumber and my contractor suggested to me and they have ZERO ties/connection to my friends. I have an exclusive FB account setup with only 7 of my closest friends and family members. This is how I knew once my plumber showed up as a suggestion that FB had to be getting into my contacts. This REALLY infuriates me. Talk about intrusive.

    • I once got a friend suggestion from Facebook for a real estate agent that I met only once and spoke on the phone. It was a phone number I never used on Facebook as it was a temporary number I only had for 2 months. Kind of freaky.


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