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Fahad Subzwari
Fahad Subzwari

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I made DuckDuckGo's invisible tracker blocking visible, here is how it looks

#webdev #javascript #privacy #opensource

How many companies do you think track you when you visit your most-used website?

I guessed maybe 5. I was wrong by a lot.

That question is what pushed me to build this.

DuckDuckGo blocks trackers silently. You never see what you were protected from. That makes it impossible to explain to someone why it actually matters.

So I built Privacy Diff, i.e., a tool that makes that protection visible, for any website.

Privacy Diff demo

Paste any URL. Two headless browsers run in parallel, i.e., one protected with DDG's actual TDS blocklist, one not. It diffs the network activity and generates a shareable report showing which trackers were blocked, which companies own them, and what category they fall under (Advertising, Analytics, Fingerprinting, Social).

The results vary a lot depending on the site. Some shopping sites are worse than news sites. Some recipe blogs carry more ad trackers than major publishers. That is part of what makes it interesting and you genuinely do not know until you look.

How it works under the hood 

Paste any URL
   |
   v
Two Chromium sessions run in parallel
   - Unprotected (baseline)
   - Blocked (DDG TDS blocklist)
   |
   v
Diff the network requests
Map each blocked domain to its company + category
using DuckDuckGo's open Tracker Radar dataset
   |
   v
Shareable report at /r/{slug} — cached weekly
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The tracker lookup is built at compile time from DDG's android-tds.json (3,092 entries). Suffix-matching resolves any hostname to its owning company in O(1).

Stack: Next.js 15, Express, Playwright, Drizzle + Postgres, Railway.

Live demo: [https://web-production-8b4e2.up.railway.app/]
Source: github.com/fahadsubzwari924/privacy-diff

Try it on any site you use daily and drop your result in the comments.

I am genuinely curious which site surprises people the most, my bet is that it will not be the obvious one.

Built independently using DDG's open-source Tracker Radar (CC BY-NC-SA 4.0)
and tracker-blocklists (Apache 2.0).

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