Shield icon in Firefox: Tracking attempts blocked

Question

When browsing sites in the StackExchange network, Firefox shows a shield by the address bar, and if you hover it it says "Tracking attempts blocked".

Yeah, you should be worried about your privacy. As for what they track, their ads collect a bunch of PII, and there's also Google analytics (pretty standard, unfortunately) and I think a third tracker (not sure, I vaguely remember a third from my list of blocked trackers) — Zoe stands with Ukraine, Sep 13, 2019 at 22:24
Users who use their Facebook avatar will also trigger this icon. — Sonic the Anonymous Hedgehog, Sep 13, 2019 at 23:49
@Olivia Quantcast and ScoreCard research beacon? i.stack.imgur.com/ywhCh.png — anki, Sep 14, 2019 at 7:55
To be more specific about Sonic's message: if a user on the current page has a loaded profile pic from Facebook, the page includes trackers from the FB graph API that Firefox blocks. Related: meta.stackoverflow.com/q/384864/6296561 — Zoe stands with Ukraine, Sep 14, 2019 at 8:22

kmg90 · Accepted Answer · 2019-09-17 20:15:58Z

Firefox now blocks cookies from third party sources that only purpose is to track the user across the web in order to "profile" based behavior patterns of users anonymously (the rise of algorithms and neural networks can predict your income, age group, hobbies just from so websites can "better serve you" (aka more "relevant" ads or "content") (see below for the upcoming improved UI of this new feature)
Scorecard Research and Quantserve are the being blocked from storing cookies that are used to uniquely identify you across multiple websites.
This comes down to what you and the owners of the websites you visit think should be able to be tracked/shared with each other
Again this is up to you.

omg, obviously you can click on the shield to get more information :facepalm:. Thank you for this kmg90. Btw, I love Firefox. I'll come back and accept the answer unless someone comes with a more "official" / authoritative answer. — aioobe, Sep 17, 2019 at 21:08

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