Difference in adblocking in Private window and normal window

Description of the issue:
I use nextdns on system level so I can see which requests are blocked by it.
While visiting https://www.macrumors.com/ in normal window, there are many domains comes in nextdns which are blocked by nextdns, but when I visit same website in Private window, those domains don’t come in logs means they are blocked by Brave. So my questions is why those are not blocked in normal window ?

To be sure that it is the case, I’ve tried 2-3 times, and as nextdns has cache, I’ve tried in normal window and private window in the interval of 10 mins, when effect of cache is gone.

Edit 1: I tested with both agrressive and standard adblock setting, same behaviour
Edit 2: I tried clearing browing data (all cookies, caches etc), same behaviour

Exact URL of the website in question:

Screenshot of the ad as it appears in Brave
In Normal Window


in Private window


Did the issue present with default Shields settings? (yes/no)
yes

Does the site function as expected when Shields are turned off?
irrelevant

Is there a specific Shields configuration that causes the site to break? If so, tell us that configuration. (yes/no):
irrelevant

Does the site work as expected when using Chrome?
irrelevant

Brave version (check About Brave):

Version 1.26.43 Chromium: 91.0.4472.77 (Official Build) beta (x86_64)

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Possibly, some tracking sites know if private window mode is set, or if they check for cookies. Either way, we’re blocking trackers in both scenarios (just checked).

1 Like

Sir, if trackers are blocked than in normal window why there are logs in nextdns (nextdns blocks those dns requests) , it shouldn’t be there right ??

Edit: I checked with Firefox, in firefox we get only 2 entries which are same as Brave in private window, means ublock + firefox blocks them in normal window also but brave wasn’t able to ??

Are not blocking enough? or are we blocking too much? Using the third-party DNS (next dns) may change the blocked results also.

Dns requests are still allowed from brave which nextdns blocks, so trackers can still track if I don’t use nextdns

I tried to figure out and find out that it is because of “dns prefetching”,
If we untick Disable pre-fetching (to prevent any connection for blocked network requests) option in ublock in firefox then we also get same dns requests from firefox in nextdns.

According to this article, chromium allows website to override user setting for “dns prefetching”, so though brave tried to block some tracking cookies/scripts/tag, website still was able to established dns requests and was able to track user (If I don’t use nextdns).

Ublock origin states that it is chromium issue.
Can brave team look at it and tried to find any solution like brave did for CNAME tracking ??

Ah right. This change would need to come from Chromium upstream, it’s not a Brave-only issue here