Hello! I recently tried NextDNS and noticed that is detects my current DNS resolved on the go. I just opened its website and it immediately showed my current resolver:
When I tried changing private DNS to Cloudflatein settings it instantly showed my new resolver.
But how exactly it works? Does the browser send used DNS server to website? Or it is done somehow via JavaScript?
And also: So every website can know what I am using now? Can it be used for fingerprinting?
this post was submitted on 06 Feb 2025
26 points (96.4% liked)
Privacy
33590 readers
861 users here now
A place to discuss privacy and freedom in the digital world.
Privacy has become a very important issue in modern society, with companies and governments constantly abusing their power, more and more people are waking up to the importance of digital privacy.
In this community everyone is welcome to post links and discuss topics related to privacy.
Some Rules
- Posting a link to a website containing tracking isn't great, if contents of the website are behind a paywall maybe copy them into the post
- Don't promote proprietary software
- Try to keep things on topic
- If you have a question, please try searching for previous discussions, maybe it has already been answered
- Reposts are fine, but should have at least a couple of weeks in between so that the post can reach a new audience
- Be nice :)
Related communities
much thanks to @gary_host_laptop for the logo design :)
founded 5 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
The website requests an image or whatever from
27748626267848298474.example.com, where the number is unique for the visitor. To load the content the browser has to resolve the DNS for it, and the randomness ensures it won't be cached anywhere as it's just for you. So it queries its DNS server which queries your DNS provider which queries the website's DNS server. From there the website's DNS server can see where the request came from and the website can tell you where it came from and who it's associated with if known.Yes it absolutely can be used for fingerprinting. Everything can be used for fingerprinting, and we refuse to fix it because "but who thinks of the ad companies???".
This is exactly what nextDNS is doing:
1sc5k91u2kx-2e5621.test.nextdns.io
Showed up in my dns logs when I opened the page, with a new random number each refresh.