Yesterday morning at home I Googled the instrument, the name of which I didn't actually know but Google came to the rescue. I browsed Google Shopping [2] but didn't purchase one.

Later I went into work where Facebook displayed an ad for the instrument in its "sponsored" section and an inline "suggested post" for a manufacturer.

My home and work computers and networks are completely different. I typically use incognito mode and "do not track" in Firefox or Chrome. I sign out of all social media and Gmail. Yesterday I was working in a large building with tens of people all using wifi used by hundreds of people across several buildings.

I assume no outright nefarious activity, such as an illicit pipe of potential customer IDs between Fb and Google.

The best I can theorise is that I had an open Fb window at home, and one of the instrument manufacturers' websites had an embedded Facebook like button or similar tracker, and they are running targeted ads on Fb. But is this direct-to-an-individual targetting even possible on Fb? Perhaps the obscurity of the instrument meant that I was very likely to see an ad, and very likely to notice it.

I typically close Fb when I'm not using it, so this doesn't immediately feel like what happened. I'll be doubly-sure to close and log-out Fb now.

I can't think of other ways that my Google activity could get to Fb. Browser fingerprinting, cellphone location etc would allow Fb to understand my location, but I can't see how they'd match this against Google activity.

I'd be very interested to read how this is, or could be, achieved.

[1] https://news.ycombinator.com/item?id=14094083

[2] https://www.google.com/shopping