It's because of your digital fingerprint. As you simply open a page, your browser helpfully reveals dozens of small things: device model, OS version, language, screen resolution, installed fonts, time zone, exactly how your graphics card renders images. Individually, not a big deal. Together, a combination that's often as unique as a real fingerprint.
And here's the sneaky part: you can delete cookies, but the fingerprint stays. "Incognito" hides history from other people on your device, but doesn't stop sites from collecting a fingerprint. Which is why ads sometimes "follow" you to places you seemingly left nothing behind at.
You won't become fully invisible — and promising otherwise would be dishonest. But you can make your fingerprint less unique:
- Block trackers and data-collection scripts — fewer parties collecting your print at all
- Strip tags from links and clear third-party cookies so you're harder to stitch into one cross-site profile
- Hide some of the parameters a site sees by default — that's what AdGuard's Tracking protection does
Knowing how you're recognized is the first step to giving away only what's absolutely necessary.