Digital Marketing

Why and How Do Ads Follow Me Around the Web?

AdsAdvertisingcookiesremarketingretargetingthird-party data sharing
Updated April 26, 2022 Wiredelta

You might have noticed how visiting a random website results in total and utter bombardment of that website’s offerings anywhere you go on the internet shortly after.


This creepy stalking tool is what digital marketers call Retargeting, and it is made possible through cookies.


Cookies remember website configuration (e.g. language preferences or dark mode), login details, and products added to the shopping cart, even after a user leaves the site, but because cookie files are widely used to collect certain pieces of information, they can also be used to carry out advertising processes like behavioral profiling and retargeting.


How do cookies work?

Before we dive into how cookies work, it is important to distinguish between first-party cookies and third-party cookies.

Technically speaking, first- and third-party cookies are the same type of files. What’s different is how they are created and used by websites.


First-party cookies are created by the host domain – the domain the user is visiting. These types of cookies are generally considered good; they help provide a better user experience and keep the session open. This basically means the browser is able to remember key pieces of information, such as which items you add to shopping carts, your username and passwords, and language preferences.


Third-party cookies are those created by domains other than the one the user is visiting at the time, and are mainly used for tracking and online-advertising purposes. They also allow website owners to provide certain services, such as live chats.


When you see an ad on, for example, from, a website you just visited, then it is due to and advertiser.compassing your cookie file between each other. The process goes like this:

1) You go to and send it your cookie file, a unique identifier of you.

2) The web server hosting takes your user ID from the cookie and sends a JSON request to to create a session for you, passing your user ID.

3) The web server outputs an image/banner/text link to with the session ID created in step 2.

4) When your browser connects to, it sends the cookie in the headers and the session ID in the URL.

5) The server hosting can now associate your session with their own user record and your user record at and it can output an appropriate ad.


A comprehensive guide is provided by Vox below, interviewing the creator of internet cookies, Lou Montulli:




How does retargeting ads work, and how is it legal?

Retargeting, more generally referred to as remarketing, is an effective strategy for converting website visitors to customers because it specifically targets visitors who have already shown an interest in a company’s product. These visitors are more likely to convert than random visitors who may have little or no desire to buy a particular product.

Remarketing and retargeting explained


Some of you out there might wonder, how is all this legal? Passing information from one entity to another without consent doesn’t sound totally legit. Thankfully, regulation is here to the rescue.


With the introduction of GDPR regulations in Europe, and similar legislation being passed worldwide, websites across the internet needs to abide to new privacy regulation. This is why you see all these cookie bars on websites across the web today:


Example of cookie consent


Surely both the web and hence new regulation will be introduced to protect our online privacy and user data. Time will tell what happens next, but you can be sure that Wiredelta is following this closely!



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