Find the trackers on a page
When you open a news article, you’re not just talking to the news site. Your browser quietly contacts dozens of other companies at the same time, and some of them recognise you from site to site. In this lesson you’ll use the tools built into your own browser to count them, find their cookies and cut them down.
In this lesson
- Watch every company a page contacts, using your browser’s developer tools
- Find the cookies a page leaves behind, and tell first-party from third-party
- Block third-party tracking and measure the difference
You’ll need: a computer with Chrome, Edge or Firefox. Phones don’t have developer tools, so parts 1 and 2 need a computer; part 3 works anywhere. You met the Network panel in The Journey of a Web Page.
First-party and third-party
The first party is the site in your address bar. Everything else the page loads from another company’s servers is a third party: adverts, analytics, social media buttons, embedded videos, fonts, chat widgets. Many of those are harmless. Some are trackers: their job is to notice the same browser on many different sites and build a profile of what it reads.
They recognise you mainly with third-party cookies, small files a tracker stores in your browser and reads back whenever another site includes it. When a cookie isn’t available, they fall back on the fingerprint you saw in Lesson 1.
Try it yourself · part 1
Count the companies one page contacts
- Open an article on a big news website, the kind with adverts.
- Open the developer tools: F12, or Ctrl+Shift+I on Windows and Linux, Cmd+Option+I on a Mac. Click the Network tab.
- Reload the page with the panel open. Watch the list fill up. The status bar at the bottom counts the requests; on a news page it’s often in the hundreds.
- Make the companies visible. In Firefox there’s a Domain column already. In Chrome and Edge, right-click any column heading and tick Domain. Click the heading to sort by it.
- Scroll through the domains. Anything that isn’t the news site’s own name is a third party. Look out for names like
doubleclick.netandgoogletagmanager.com(Google’s advertising and tags),facebook.net(Meta’s tracking pixel),criteo,taboolaandoutbrain(advertising and “recommended stories”). - Count roughly how many different companies appear. Write the number down; you’ll compare it in part 3.
Try it yourself · part 2
Find the cookies they left
- Still in the developer tools, open Application (Chrome and Edge) or Storage (Firefox), then Cookies in the list on the left.
- You’ll see the site’s own address, and often others underneath it. Each extra entry is a third party that stored, or tried to store, a cookie while you read one page.
- Click one and look at the cookie names and their Expires dates. Tracking cookies often last a year or more.
- You don’t need to understand the values. The point is the shape of it: one visit, many companies, cookies that outlive the visit.
Curious about ours? On examineip.com you’ll find two: Umami, which counts visits without cookies, and Google’s tag, which sets no cookies unless you accept them in the cookie banner.
What your browser already does
Browsers differ a lot here, and the default matters because most people never change it:
| Browser | Third-party cookies by default |
|---|---|
| Safari | Blocked for cross-site tracking (Prevent cross-site tracking is on) |
| Firefox | Known trackers blocked, and every other site’s cookies kept in a separate jar per site (Total Cookie Protection) |
| Chrome | Allowed. Google dropped its plan to remove them, so blocking them is up to you |
| Edge | Known trackers limited by Tracking prevention, set to Balanced |
Try it yourself · part 3
Cut them down and measure the difference
- Turn on third-party cookie blocking. In Chrome: Settings → Privacy and security → Third-party cookies → Block third-party cookies. In Edge, search the settings for tracking prevention and choose Strict. Firefox and Safari already do most of this, but Firefox’s Strict setting under Privacy & Security goes further.
- For a much bigger effect, add a reputable content blocker: uBlock Origin in Firefox, or uBlock Origin Lite in Chrome and Edge. Both are free and open source, and they block trackers and adverts before they load.
- Go back to the same news article, open the Network panel and reload. Count the companies again. The drop is usually dramatic, and the page often loads faster too.
- If a site breaks, for example a video or a login stops working, you can switch the blocker off for that one site from its toolbar icon.
One more setting: tell sites not to sell your data
Global Privacy Control is a signal your browser can send to every site, asking it not to sell or share your data. Some laws, including in California and Colorado, require sites to honour it. Brave sends it by default; in Firefox it’s a tick box under Privacy & Security called Tell websites not to sell or share my data. The Privacy signals line on our What We Know page shows whether yours is on.
Key takeaways
- A single page can contact dozens of companies; the Network panel shows every one.
- Third-party cookies let trackers recognise your browser across different sites.
- Safari and Firefox block most cross-site tracking by default; Chrome doesn’t.
- Blocking third-party cookies and adding a content blocker cuts the number of companies sharply.
- Global Privacy Control asks sites not to sell your data, and some laws make them listen.
Check yourself
Three questions. Pick one answer each and you’ll see why.
1. You’re reading news.example.com, and the Network panel shows requests to doubleclick.net. What is doubleclick.net here?
2. Why do third-party cookies matter more for privacy than the site’s own cookies?
3. Which browser allows third-party cookies by default in 2026?
Want to go further? How to Become Anonymous Online puts trackers in the bigger picture, alongside your IP address and accounts.
This lesson is part of the free course Privacy and VPNs, licensed under CC BY-NC-SA 4.0: you may share and adapt it for non-commercial use, with credit to ExamineIP and a link to the original.