How Server-Set Cookies and User IDs Improve Conversion Tracking

Cookies and User IDs are fundamental to conversion tracking but play different roles in tracking user behaviors. These nuances have unique implications for the performance of your marketing campaigns. 

On an episode of the Conversion Tracking Playbook Podcast we explain how server-set cookies and User IDs impact your marketing campaign ROI.  

Listen to Episode 72 of the Conversion Tracking Playbook Podcast, or keep reading to learn how server-set cookies and User IDs improve conversion tracking: 

• What Is a Cookie? 
• Why Cookies Are Important to Marketing Platforms 
• The Difference Between a Client vs. Server-Set Cookie 
• What User IDs Are and Why They Matter 
• How to Recognize More Returning Users 

What Is a Cookie? 

A cookie is a text file containing bits of unique data that make it possible to identify a user’s device and network, and are also sometimes called browser cookies or web cookies. 

To simplify the concept, think of a cookie as a label or a barcode number in your browser. 

Cookies play a fundamental role in the way tracking works. They make it possible for websites to store users’ language preferences, cart details, and login information.  

Cookies don’t last forever. Cookies expire because of browser restrictions, which originated from browsers aiming to protect user privacy.  

To see a browser-by-browser breakdown of cookie expiration limits, check out cookiestatus.com. 

Why Cookies Are Important to Marketing Platforms 

Cookies are important to marketing platforms because of conversion tracking.  

Let’s use Facebook as an example to illustrate why cookies are important.  

When a user clicks on your brand’s Facebook ad, a piece of code called a tracking parameter is added to the URL – which is essentially a label that uniquely identifies the click.  

This label gets stored in the cookie, which goes from the URL to a browser – linking the clicks from your ad to the user’s activity on your website.  

When the cookie expires, clicks can no longer be linked to conversions that originate from your ad. 

Another reason why cookies are important is because when marketing platforms have more conversion data, they can build better audiences.  

Let’s continue our Facebook example. Facebook wants to match views and clicks on their platform to on-site activity because this helps them better report on ad performance. 

This also helps drive efficiency in terms of bidding on Facebook’s ad auction, which is: 

Bid X Estimated Action Rate X Ad Quality = Total Value 

Facebook uses the data that advertisers on their platform transmit to them to determine how likely it is that a user will convert from their ads.  

The more conversion event data Facebook has, the better they’re able to gauge the estimated action rate.  

This helps Facebook put the ad in front of audiences who are more likely to convert – boosting revenue for Facebook and the advertiser alike.  

Learn more about optimizing Facebook ads with better data collection. 

The Difference Between Client-Set Cookies vs Server-Set Cookies 

A client-set cookie is a cookie created by the client (also called the browser) via JavaScript running on a webpage. Browsers typically expire client-set cookies after 24 hours. 

Server-set cookies, on the other hand, are cookies that a server sends when they respond to the client’s request. Cookies that are set from the server can last up to a year depending on the browser. 

A key nuance between cookies that are set client-side vs server-side is that you can only set cookies server-side from the server that is hosting the website. For example, nike.com can only set the cookie command from nike.com. 

Browsers look at how cookies are set to determine how long the expiration window will be – whether that’s 24 hours or a year. 

What User IDs Are and Why They Matter 

User IDs are a unique group of numbers or letters that are attached to a unique user profile. Think of a user ID as a license plate number for an individual user.  

When you track a user’s behaviors through server-set cookies, assigning a unique user ID to the user’s data can help you recognize when that person comes back.  

User IDs allow you to build a profile of a user based on their activity and link multiple sessions and behaviors to that individual. 

Imagine the following scenario: A user visits your website anonymously – they haven’t created a login or provided any contact information, but your server-set cookies are tracking the products they view on your website. You assign a unique user ID to this data. 

A month later, this same user visits your website again and completes a product selection quiz, providing their name and email address in the process.  

Because you assigned a user ID when they first visited your website and because the cookies haven’t expired, you can link the products they viewed a month prior to this person. 

User IDs are especially helpful for abandonment flow campaigns, such as in Klaviyo. An add-to-cart event is useless data to send to Klaviyo if there’s no identifier, and cookie expirations hinder Klaviyo performance.  

Your Google Ads campaigns can also benefit from user IDs. User IDs help Google match anonymous conversion events to actual people, which can help Google Ads put your ads in front of audiences who are more likely to convert. 

How to Recognize More Returning Users 

In addition to leveraging server-set cookies and user IDs, another way to recognize more returning users is to leverage Elevar’s Session Enrichment capability.  

Through Session Enrichment, Elevar captures user-identifiable information (email address, phone number, first name, last name, etc.), stores it on our own servers for a year, and sends that data to your destinations.  

For every server event that we send, we check to see if there’s user information that matches a previous server event. If there’s a match, we will enrich all server events going forward with user-identifiable information. 

Brands that have Elevar see significant results. Users with the Elevar server-side integration for Klaviyo see 50%-60%+ more revenue, and those with the server-side integration for Meta improve Facebook ad performance by 20% or more. 

Never Miss Another Conversion 

Ready to trust your data? Book a call with us to explore how Elevar seamlessly integrates with over 20+ server-side integrations. 

We are committed to building tools to help Shopify stores increase sales and leverage customer insights for higher revenue.