I support IT systems for office with 2 workers. Both workers use Macbooks on LAN. The only other things on LAN are router and printer. The only shared login the workers have is a Dropbox account. Worker A does not have a Facebook account. Worker B has a Facebook account. Things Worker A searches for on internet (eg office supplies) promptly appear in Worker B's Facebook ads. I can't figure out how Worker B's Facebook knows what Worker A is searching for. Any ideas?
They are using same public ip address I guess. Is quite strange because usually, Google/Facebook shouldn't track your ip for many reasons:
- Because Ip addresses cannot reliably identify an individual user, advertising services track visitors through small files on their browsers called cookies.
- When you visit a website that is advertising with Google AdSense, it tells your Web browser to create a cookie with data to identify you as a unique visitor
Anyway, Google's advertising services is a "mistery" how it works and Google change its mechanisms constantly, like for SEO. Is like the "Coca Cola's secret". I've been in courses about SEO and they teach to you a lot of techniques to improve it and they work, but nobody knows 100%. There is always a small uncertainty factor.
So, usually the Ip addresses are don't used to track visitors, but if you are pretty sure this is happening, maybe Google changed something. Maybe they do use a visitor's current IP address to help select ads.
EDIT Yes, I can confirm it. I found this link on Google Documentation. Look at the paragraph which say:
Even if you opt out of Ads Personalization, you may still see ads based on factors such as your general location derived from your IP address, your browser type, and your search terms
EDIT2 Thanks @TTT for your comment. You are right. Anyway, Facebook ads works in similar way like Google ads.