What is Cookie Syncing?

Cookie syncing, or cookie matching, is a technique in adtech that allows different platforms to exchange user data and collaborate. For example, DSPs (demand-side platforms), SSPs (supply-side platforms), DMPs (data management platforms), and ad exchanges can share user IDs and preferences. This enables them to deliver more personalized and targeted ads to users across devices and web pages.

Cookie syncing creates a more comprehensive profile of a user’s interests and behavior based on their browsing history and search queries. This helps advertisers design more effective ad campaigns and reach their desired audiences. It also improves the user experience by showing them more relevant ads on different platforms.

To illustrate how cookie syncing works, let’s take a fictional user, Jacob, who wants to buy a certain type of television. He searches for “best televisions in 2023” on a search engine like Google or Bing and clicks on one of the results. His browser receives tracking cookies from the webpage and sends them to a DSP. The DSP stores his user ID and syncs it with a DMP and an ad exchange. These platforms exchange his data and preferences through redirects and parameters.

Now, the DSP can use this information to retarget Jacob with personalized ads as he browses other websites. For instance, he might see ads for televisions on an ad network or in his shopping cart while visiting another site. 

What Are Cookies?

When a user visits a website, their web browser creates and saves text files on their device (such as a computer or a smartphone). These files store information that tracks and remembers the user’s preferences and activities on that website. Cookies are necessary for the personalization and functionality of websites.

The user’s device receives and stores a cookie from the website’s server when they visit a website. The cookie is sent to the user’s browser by the server. The next time the user visits the same website, the browser and the website exchange the cookie information again. This allows the website to deliver a customized experience to the returning user.

This information could include the products you searched for on the website, the ones you clicked on, the ones you added to your cart, and the ones you bought successfully.

First-Party Cookies

First-party cookies are cookies that are created and stored by the websites that users visit frequently or occasionally. These cookies are domain specific, meaning they can only be accessed by the website that created them. Users visiting these websites can use first-party cookies to enhance their experience with personalized features.

First-party cookies do several things for the user’s browsing experience. They can remember your preferred language, font size, color scheme, and region for browsing. They can also remember your login details, checkout information (such as your name, address, and payment methods), and shopping cart items. They can also personalize your experience by showing you products you have viewed or might like based on your interests.

Third-Party Cookies

What are third-party cookies? They are cookies that are created and stored by domains that are different from the ones that users visit. These cookies are not domain specific, meaning they can be accessed by multiple websites that use the same third-party service. These cookies are usually generated by javascript code embedded in web pages.

Third-party cookies track browsing behavior and collect data about your interests and preferences. They assign you a unique identifier called a cookie ID, which creates a user profile based on your online activities. They track the websites you visit, the pages you view, the links you click on, and more. This helps them deliver targeted advertisements to you in the future.

Third-party cookies are also used to remember your login information across multiple websites. For example, if you use your Google account to log into one website, you can use the same account to log into other websites that use Google as an authentication provider.

Are Cookies Important For Digital Advertising?

Cookies are essential for the functionality and personalization of websites and digital advertising. They enable advertisers to collect and use data about your browsing activities, preferences, and interests. This data helps advertisers to deliver targeted ads that should benefit both them and you.

Cookies enable digital advertising technology such as RTB (real-time bidding), where advertisers bid for ad space on websites in real-time. When you visit a website, a bid request is sent to a DSP (demand-side platform), which is a platform that buys ad space on behalf of advertisers. 

The bid request contains information such as the DSP’s ID, the website’s URL, and the user’s cookie ID. The DSP uses this information to decide whether to bid for the ad space and how much to bid. The DSP communicates with the website through an API (application programming interface).

Advertisers can use cookies to create more relevant and personalized ad campaigns and increase conversions because of third-party ads. 

Third-party cookies are losing their value due to privacy issues and regulations. This raises the question: how will third-party cookie depreciation impact ads? It will affect how advertisers can track and target users across different websites and devices. Advertisers will need to look for alternative methods to collect and use user data for digital advertising.

Advantages of Cookie Syncing

Cookie syncing is a technique that enables different platforms to exchange user data and collaborate. It has three main benefits for marketers: retargeting, internet and demographics targeting, and excluding converted users. These benefits allow marketers to deliver more personalized and relevant ads to users based on their browsing behavior and location. 

We’ll explain these benefits in more detail in the following sections. 


Retargeting is one of the key advantages of cookie syncing and its main purpose. Cookie syncing is essential for identifying which users have visited a website or shown interest in a product. Without cookie syncing, retargeting would be very difficult.

When a user lands on a website, the cookies track their actions and preferences, collecting useful information about the pages they view and what they do on those pages. This information helps marketers to understand user interests.

To perform retargeting, marketers sync their cookies with retargeting platforms or DSPs (demand-side platforms), which are platforms that buy ad space on behalf of advertisers. Through this syncing, the platform can match the website user’s data with their own data, delivering the right ads to the right person.

Retargeting aims to increase conversions, persuading users to take specific actions like buying a product or signing up for a service. It allows customized ads to appear for those who have already shown interest, guiding them toward the desired outcome of the web platform.  

Internet and Demographics Targeting

Internet and demographics targeting are other reasons for marketers to collect user data. This allows them to analyze their browsing behavior as well as their geographic locations.

For example, knowing a user’s geographic location (based on their IP address) allows marketers to see which areas have the most visitors and customers. This could help them to adjust their advertising campaigns to specific regions and users with specific needs.

This demographic data also reveals users’ ages, genders, and various interests. All of these factors can help marketers segment their audience and deliver more targeted and relevant ads. 

Excluding Converted Users

The practice of excluding converted users is another benefit of cookie syncing. This means users who have already bought a product or signed up for a service are excluded from further ad targeting.

Through cookie syncing, publishers can match their data with that received from other platforms, such as data providers or advertising technology providers. This allows them to see who has already purchased or completed an action.

With this data, they can save time, money, and resources by excluding these users from receiving more promotional material related to the product or service. This is another way to personalize the user’s ad experience and improve their satisfaction with your website. 

Disadvantages of Cookie Syncing

Cookie syncing has some significant drawbacks that need to be considered. These include privacy concerns and data leakage, errors or failures in the data transfer during cookie syncing, latency, or slow page loading times due to third-party redirects. 

In the following sections, we’ll examine these three drawbacks in detail, ensuring you clearly understand what they can mean for your website or your user experience. 

Privacy & Data Leakage

Privacy and data leakage is the most common drawback of cookies. Users are becoming more aware of the potential risks of sharing their data on various websites. In some cases, they may use ad blockers that prevent websites from accessing this data. 

Many users do not like the idea of their browsing data being shared across websites without their explicit consent. This becomes a more significant concern when that data is unlawfully leaked or disclosed without permission from the concerned party. This kind of leakage can happen with third-party cookies when sharing data across platforms. 

Several measures have been taken to make this privacy violation less common. For example, the GDPR (General Data Protection Regulation) is a regulation that protects the data and privacy of users in the European Union. The IAB (Interactive Advertising Bureau) is an organization that sets standards and guidelines for online advertising. But there are still concerns have made users wary of cookies in general. 


Possible errors in data are also an important drawback of cookies. These errors occur in a few different situations. For example, when a user interacts with multiple websites, the cookies are overwritten. 

The new data may replace old data, or the new data is not correctly updated to the user’s profile. This may mean that target advertising goes wrong. Someone might see ads that are no longer relevant or have no connection to their interests. 

There can also be errors when using cross-device tracking. For example, remembering the user data as they move from their smartphone to their tablet to their computer. In some cases, cookie syncing fails in transferring the data correctly, and users may find that their login data, saved items, and more are not transferring between their smartphone and laptop. 

Another possible situation happens when users’ behavior changes over time. For example, if someone’s interests change and they are no longer interested in the same products or services they were before. 

This can mean that they are served the wrong ads for a long time. As with these other errors, this incorrect ad data may drive the user away if they constantly see uninteresting and irrelevant advertising that has nothing to do with their interests. 

Lastly, it’s essential to consider how limited contextual data can make cookies inaccurate. For example, someone might visit a website for work but have no interest in the advertised product. If they’re continually shown ads for something they don’t care about, the website will waste resources in the long run. 


Latency is another issue. It refers to the time delay between a user’s request on a page and the response from the server. When a website uses a lot of third-party redirects, it can increase the page load time. This can, therefore, create a slower loading time as the user moves from page to page and an overall bad user experience. 

When this happens, a website might end up driving away more traffic than they are converting into revenue. Slow pages can be incredibly frustrating to users, and the many different online resources make it more likely that they will turn to a competing website with faster page load times. 

Slow page loading times can also impact your Google ranking and overall SEO. So it’s important to ensure that your cookies are operating properly and that you don’t have too many third-party redirects impacting your page loading time. 


To summarize, cookies are small files that store users’ data. This data includes their online behavior, interests, and the websites they visit. Cookies play a vital role in customizing user experience and can do everything from remembering login data to target advertising and more.

Cookie syncing is a technique that enables different platforms to exchange user data and collaborate. It allows advertisers to deliver more personalized and relevant ads to users across devices and websites.

There are many benefits and a few significant drawbacks to cookies and cookie syncing. The drawbacks include data leakage, errors, and latency, while the benefits include better conversion rates, a more relevant ad experience, and more.

Here at Newor Media, we know it’s very important to use cookies and cookie syncing in digital advertising while protecting user privacy and data. We ensure that data is handled responsibly and that all our practices comply with privacy regulations, creating a secure and trustworthy ecosystem.

Interested in how much your website could potentially earn? Check out our earnings calculator. Using our ad network, you can successfully create advertising campaigns while upholding user privacy and delivering the right content to your audience. 

Lauren Aloia

Senior Account Manager, Publisher Development: Newor Media

Lauren is an ad tech expert with a wealth of experience spanning product development, ad operations, and data analysis. She currently works with Newor Media publishers to implement yield optimization strategies that maximize revenue from their programmatic inventory.