Syllabus Lesson 6 of 156 · What a website knows the moment you arrive
What a website knows the moment you arrive

Quiz and recap

Why it matters These questions check that you can now look at any page and say what it learned about you on arrival. You can retry as often as you like; nothing leaves your device.

What you learned in this module

  • Headers and scripts: the server sees your IP address and headers such as User-Agent and Accept-Language; the page's scripts can read screen size, time zone and more.
  • IP addresses: they point at a network and a rough place, not at your name.
  • The referrer: it tells the next site where you came from; Referrer-Policy limits it, and browsers now default to sending only the origin to other sites.
  • Link decoration: labels like utm_, fbclid and gclid ride along in links; you can clean them.
  • WebRTC: local addresses are hidden by mDNS, but the public address can still be learned through STUN.

Recap

  • A site knows your device and network before you do anything.
  • Most of these details have honest uses; collecting and joining them is the risk.
  • You can see all of it yourself in DevTools, and limit some of it.

Spotted a problem in this lesson? Report it

Code · runs in your browser
Output

        

      

      
      

        Back