Facebook was doing tracking pixels in the 00s. It probably worked even better then because stuff that's currently in apps was on the web back then and fewer pe

Facebook was doing tracking pixels in the 00s. It probably worked even better then because stuff that's currently in apps was on the web back then and fewer people ran adblockers. Every party in the advertising ecosystem should be assumed to be doing this (and your adblocker should be trying its best to block it).