5 minutes ago I visited a book store website. A few minutes later I browse another site, It shows me some advertise about books.

How can they do that?

That is about retargeting marketing. There are some techniques to track you on the internet, they will know your habits, your browsing history,…

Base on these records, it might know that you might pay attention to.

Here are a few techniques they often use on the internet:

IP Address

Everyone has a public IP address, It can be used to identify where are you from or who you are.

HTTP Referer

If I’m at a facebook page, I click a link to https://hungdoan.com

A web browser will add an HTTP Referer header to the request with value =”facebook.com”. Then I’m the owner of  https://hungdoan.com, I will know that you accessed by page via facebook. I know that you are using Facebook, that might be very useful for me in the marketing plan.

Cookies & Tracking Scripts

Because cookies cannot be removed when you close web browsers.

Cookies can be used as an identity to track who you are.

Tracking script is about you use a service from the third party like Facebook Like, Facebook Comment, Google Analytics, Chat box,…when you use them, these company will know what site you are browsing!

Super Cookies

Super cookies are about storing a piece of data on your web-browser permanently.

It’s not cookies, but It having the same purpose “store data”.

Super cookies are generally more difficult for users to detect and remove from their devices because they cannot be deleted in the same fashion as regular cookies.

User Agent

When you open a web page. Web Brower will attach User Agent to the request. It will tell the web server about which OS you are using, which version of Web Browser you are using.

Browser Fingerprinting

“A device fingerprint, machine fingerprint or browser fingerprint is information collected about a remote computing device for the purpose of identification. Fingerprints can be used to fully or partially identify individual users or devices even when cookies are turned off.”

That means that, when you connect to the internet on your laptop or smartphone, your device will hand over a bunch of specific data to the receiving server about the websites you visit.

Browser fingerprinting is a powerful method that websites use to collect information about your browser type and version, as well as your operating system, active plugins, timezone, language, screen resolution, and various other active settings.

This information can be used to identify who you are.

Ref: https://www.howtogeek.com/115483/htg-explains-learn-how-websites-are-tracking-you-online/