I found this paper interesting [1] and how they characterize Firefox' behavior out of the box:
We investigate the request behavior of each browser
(Figure 7). Brave is the most effective at reducing third-
party tracking-and-advertising requests; its claim to (1)
is supported. The other privacy-focused browsers vary
significantly in terms of reducing third-party tracking-
and-advertising requests. Firefox Focus and Ghostery
differ significantly in how much they reduce third-
party tracking-and-advertising requests, but the perfor-
mance of both supports their claims, (1) and (2). Fire-
fox is least effective at reducing third-party tracking-
and-advertising requests. This is unsurprising, as Fire-
fox’s enabled-by-default “standard” tracking protection
“blocks fewer trackers” [79]. It errs on the side of caution
in what it blocks, focusing on restricting tracking cook-
ies, social-media trackers, and fingerprinting scripts; it
does not block other content (loaded ads, videos) that
may perform tracking [78, 105]. Thus, while Firefox
claims (2), its blocking of tracking and advertising is
limited with its default settings.
This is quite disappointing given Mozilla's marketing around privacy.
- Tracking Protection basically blocks connections to known trackers entirely so the resources don't even load.
- Enhanced Tracking Protection prevents various kinds of cross-site tracking by blocking cookies, etc. (https://support.mozilla.org/en-US/kb/enhanced-tracking-prote...).
ETP is on by default. TP is not.