Comment by AshamedCaptain

So you take literally the worst possible set of IPs (all of them cloudflare), IPv4 only, and yet Copilot (!) is easily able to reverse 50% of them:

  104.21.3.245 -- trebaol.com
  104.21.80.31 -- diwank.space
  104.26.4.133 -- daringfireball.net 
  104.21.112.1 -- simonwillison.net , taras.glek.net

This was literally the worst example you could possibly do. I hope you kept which one was which, I'd like to know if Copilot was right.

In the meanwhile, from the current top #30 articles on HN (also via copilot script, but I removed non-cloudflare IPs):

  ycombinator.com -- no CDN
  letsbend.de -- no CDN
  grepular.com -- no CDN
  xania.org -- cloudfront
  github.io -- no common CDN
  owlposting.com -- AWS, but IPv4 remained static
  netfort.gr.jp -- no CDN
  simonwillison.net -- cloudflare, 104.21.112.1 fixed
  folklore.org -- azure, 13.107.246.1-255 range
  danq.me -- no CDN
  nature.com -- fastly, IPv4 remained static
  daringfireball.net -- cloudflare, 104.26.4.133
  ssp.sh -- no CDN
  trebaol.com -- cloudflare, 104.21.3.245
  glek.net -- cloudflare, 104.21.112.1
  gov.uk -- AWS, but IPV4 remained static
  phys.org -- no CDN
  diwank.space -- cloudflare, 104.21.80.31 
  free.fr -- no CDN   (my French ISP, btw)
  ericgardner.info -- AWS, but IPv4 remained static
  ghuntley.com -- fastly, IPv4 remained static
  paavo.com -- no CDN
  railway.com -- cloudflare, 104.18.24.53
  alloc.dev -- cloudflare , 188.114.96.2

Look at how many of them are self-hosted, have zero CDN, or otherwise return me always the same IP (even when I try from 3 different ISPs) which makes them trivial to reverse address. This is already a pretty huge success rate and all my context is that you browsed HN first (which I know, see first result on the list). Now imagine the tools a ISP will have at its disposal:

- IPv6

- Its Geo region will actually match yours

- Routing tables

- The patience to also include resources fetched from these pages in the analysis (i.e. page X always gets its JS from Y domain which results in a constant Z KB transfer).

- The rest of your browsing activity

- The rest of everyone's browsing activity including most popular _current_ hosts for each hostname.

Do you still claim that it is "impossible" to track your activity because of CDNs? I still bet you your ISP can do it with _100%_ accuracy.