Cookies can be read by other servers and advertising networks use them to identify your computer, and to serve up ads based on what you've been looking at.
Not accepting cookies from third party servers, or switching to private browsing mode which limits and deletes them after you leave a site puts spanners in the wheels of the trackers who now have less information about you.
The trackers work around that by collecting information that your browser sends out about your device and add its internet protocol address, time zone and other data to uniquely identify you.
This is known as fingerprinting, and Apple will limit the information that's being sent out to make it harder to identify you. But wait, there's more, much more.
Devices have unique identifiers that app developers can collect.
These IDs can be associated with online accounts, and other devices, to build a more complete and accurate profile of your habits and the gear you use.
For instance, if you visit a site with a pricey iPhone X or Samsung Galaxy GS9 Plus, it's a safe bet you're in a wealthy demographic.
Then there are the social media "Like" and "Share" buttons that will tell advertising platforms when you visit sites even if you don't click them, and make use of data collected associated with you collected elsewhere to dish up those personalised ads.
Is this creepy? Maybe, but it's a computer algorithm doing it, not a person, and it's not malicious as such.
What's best here? Being tracked and getting ads about things you're actually interested in, or being bombarded with irrelevant ones?
For advertisers, tracking and targeting are make-or-break features especially for smaller brands that would otherwise drown in the sea of internet-borne offerings.
Advertising platforms like Facebook and Google would be useless for brands without targeting, and possibly really annoying to users as well.
The problem here is that like with most things related to internet advertising, targeting is done badly and inconsiderately.
Sometimes you want to be tracked and served relevant ads, other times you don't.
Insensitive computer algorithms can't tell which and when they get it wrong, people feel violated and fire up ad blockers in vain to protect their privacy.
What it boils down to is lack of informed consent from users, and transparency by internet data gatherers.
Advertising at internet scale means vast amounts of reasonably accurate information on what almost everyone in the world cares about, from business and socio-economic issues to politics and religious matters, is collected every second.
Google, Facebook and other internet giants' ability to collect so much information on the world population gives them power beyond that of Governments, in a way we have never seen before.
In the light of that, you'd have to ask how much Apple's efforts or even the EU's GDPR privacy regulation will help and if breaking up large internet companies is the answer instead.
