Firefox State Partitioning

State Partitioning is an interesting privacy feature shipping with Firefox 86.

With State Partitioning, shared state such as cookies, localStorage, etc. will be partitioned (isolated) by the top-level website you’re visiting. In other words, every first party and its embedded third-party contexts will be put into a self-contained bucket.

Applies to every embedded third-party resource (regardless of whether it is a tracker or not), but some exceptions for Single Sign-On purposes have been made.

Firefox State Partitioning →

As of version 85 a similar feature landed in Chromium. Safari introduced partitioning for Cookies with its Intelligent Tracking Prevention 1.0. Can’t find any mention whether Safari also partitions other 3rd-party content, but I think they do.

☝️ Without these protections, ads follow you around the internet.

Why The Web Is Such A Mess

Video by Tom Scott on 3rd party cookies and tracking and what not.

How ads follow you around the internet

A video-version of How tracking pixels work by Vox:

In this video, we explain how cookies work and what you should know about how they’re being used. And we get a little help from the man who invented them.

Spot on “Finding Dory” analogy. One thing where they do go off a bit is that they somewhat imply that all data (such as shopping cart contents) is stored in the cookies themselves. That’s not the case: the cart contents are – or at least they should be – stored on the server. Only the cart’s ID (or your visitor/session ID) is stored in the cookie. The serverside code will then use that ID to get your card contents.

Also: would have loved to see a few examples with actual mentions of domain names to have it more clear.

How tracking pixels work

Julia Evans:

I spent some time talking to a reporter yesterday about how advertisers track people on the internet. We had a really fun time looking at Firefox’s developer tools together (I’m not an internet privacy expert, but I do know how to use the network tab in developer tools!) and I learned a few things about how tracking pixels actually work in practice!

How tracking pixels work →

💡 You might also want to read up on first and third party cookies