I googled from incognito Mobile Firefox a specific brand's specific mattress cover, and visited its listing on the websites of various retailers. Since nobody h

I googled from incognito Mobile Firefox a specific brand's specific mattress cover, and visited its listing on the websites of various retailers. Since nobody had it in stock locally, the next day I ended up ordering the item from Amazon. A day later, I was browsing Facebook on my home desktop and saw an ad for the exact same item in my feed. It's likely they partner with data brokers of credit card companies for your purchase history. For me, this is the only explanation, as I did not talk about the item out loud, and have no mic-enabled Facebook-owned app on my phone in any case. As a low-tech solution, correlating IP addresses with "suspected companion device" is also likely.