Third-Party Cookies

Third-party cookies zijn kleine trackingbestanden die niet door de website zelf worden geplaatst, maar door externe partijen zoals advertentieplatforms, analysebureaus of social media-netwerken. Deze cookies volgen je websitebezoekers over meerdere domeinen heen en verzamelen gegevens over surfgedrag, interesses en conversies. Voor MKB-bedrijven betekent dit dat je remarketing kunt inzetten, conversies kunt meten en doelgroepen kunt opbouwen. Tegelijk verdwijnen third-party cookies geleidelijk uit alle grote browsers vanwege privacywetgeving en gebruikerscontrole.

How third-party cookies work technically

When your website loads an ad pixel or tracking script from Google Ads, Meta or another platform, that external domain places a cookie in your visitor's browser. That cookie is given a unique identifier that is linked to that user's profile within the ad platform. If that same visitor later visits another website with the same tracking script, the platform recognizes the cookie and records that behavior. This creates a cross-site profile. First-party cookies, on the other hand, are set by your own domain and are limited to your site. The difference is in the domain that sets the cookie, not the technology itself. Modern browsers such as Safari and Firefox block third-party cookies by default. Chrome had also announced this for 2024, but has postponed that deadline.

Why third-party cookies came into being and why they are disappearing now

In the 1990s, ad networks used cookies to optimize campaigns and reduce frequency. Advertisers could thus prevent the same person from seeing the same banner 20 times. Later, tracking evolved into detailed profiles with interests, purchase behavior and demographics. This provided more effective ads, but also raised privacy concerns. The Personal Data Authority and European legislation such as the AVG and ePrivacy Directive force websites to ask permission for non-essential cookies. Browser manufacturers are responding with Intelligent Tracking Prevention, Enhanced Tracking Protection and similar blockers. The result is that third-party cookies will become largely unusable for advertising purposes within a few years.

What third-party cookies bring to SMBs

Als je online marketing inzet via Google Ads, Meta of LinkedIn, zijn third-party cookies nog steeds de ruggengraat van je remarketing-campagnes en conversie-attributie. Je kunt bezoekers die een productpagina bekeken maar niet bestelden opnieuw bereiken met een gerichte advertentie. Je meet welke advertentie tot een aankoop leidde, ook als die aankoop dagen later plaatsvond. Je bouwt lookalike-doelgroepen op basis van je bestaande klanten. Voor een webshop met een gemiddelde orderwaarde boven 100 euro kan remarketing de ROI van je advertentie-uitgaven verdubbelen. Tegelijk moet je nu al alternatieven voorbereiden, zoals first-party data en server-side tracking, omdat third-party cookies binnen afzienbare tijd niet meer beschikbaar zijn in de meeste browsers.

Third-party cookies are used in practice for ad targeting, conversion tracking and cross-site analysis. Although the technology is being phased out, many SMBs still rely on it today for their online marketing. Below you can see the main uses and when they make sense or not.

Remarketing and retargeting to previous visitors

An ecommerce store with 5,000 visitors per month and a 2 percent conversion rate sees 4,900 people leave without a purchase. With a third-party cookie from Google Ads or Meta, you can reach those visitors again with an ad for the product they viewed. You create a target audience of everyone who visited a product page in the last 30 days but did not checkout. That target audience gets a specific ad with a discount code or social proof. Remarketing often yields a three to five times higher conversion rate than cold traffic because the visitor already knows your brand. The cookie allows the ad platform to recognize the visitor on other websites. Without a third-party cookie, you lose that ability unless you switch to first-party data and a customer data platform.

Conversion tracking across multiple sessions and devices

A B2B service provider with a two- to six-week sales journey wants to know which ad or keyword ultimately led to a quote request. Third-party cookies from Google Ads record the first click on an ad and link it to a conversion that occurs days later. If the same user clicks on desktop and later converts on mobile, the platform tries to link those sessions via cross-device tracking. That only works if the user is logged into Google or if the cookie is present on both devices. In practice, cross-device tracking is incomplete, but third-party cookies still provide the best attribution for single-device journeys. Without these cookies, you can only measure last-click attribution through your own analytics, which gives a distorted view of your marketing channels.

Audience segmentation and lookalike audiences

An online course platform wants to find new customers similar to existing buyers. Using third-party cookies, Meta builds a profile of your existing customers based on their browsing habits, interests and demographics. That profile is compared to all Facebook users, then Meta builds a lookalike target group of people with similar characteristics. Your ads are shown to that group, increasing the likelihood of conversion. This technique only works if Meta has enough third-party data on your existing customers. Once browsers block third-party cookies, the data set becomes smaller and less accurate. An alternative is to upload a customer list of e-mail addresses, which Meta matches with logged-in users. That is a form of first-party data integration and often requires customization.

When third-party cookies are the right choice and when they are not

Third-party cookies make sense now if you are actively advertising through Google, Meta or LinkedIn and want to remarket or measure conversions. They don't make sense if you're only using organic channels, if your target audience is primarily Safari or Firefox users, or if you're building a long-term strategy without reliance on third-party platforms. A mistake many SMBs make is not preparing an alternative. Start now by building your own email list, implementing server-side tracking and collecting explicit consent for first-party cookies. That way you will remain measurable and targetable even after third-party cookies end.