The Case for a First-Party Cookie Approach in Online Advertising

The debate over the long-term role of third-party cookies in digital advertising has been ongoing for years. Some argue they remain a necessary fixture of the online advertising ecosystem; others contend they're on borrowed time, squeezed out by the rise of ad blockers, browser-level privacy restrictions, and cross-device tracking technologies that could eventually make them redundant.

Whatever your position, the practical argument for adopting a first-party cookie approach is compelling — for advertisers, marketers, and ad tech operators alike. This article covers what distinguishes first-party from third-party cookies, the concrete benefits of the first-party approach, how to implement it, and where its limits lie.

What Are First-Party and Third-Party Cookies?

Cookies are created each time a user visits a website. Often, both a first-party and a third-party cookie are generated in the same session. The key difference is who creates them.

First-party cookies are set by the website a user is actively visiting. If someone reads articles on CNN, the Huffington Post, and the New York Times, each of those sites sets its own cookie and stores it in the user's browser.

Third-party cookies are set by parties other than the site the user is visiting. Take CNN as an example: CNN sets a first-party cookie, but the ads displayed on the page — served through an external ad network or DSP — also set cookies, typically under a domain like ads.somedsp.com. Because those cookies don't originate from CNN, they're classified as third-party cookies.

Third-party cookies are deeply embedded in how programmatic advertising works, but they come with a growing list of vulnerabilities. Specifically, third-party cookies are blocked when a user does one or more of the following:

• Browses in private or incognito mode.
• Uses Safari on Apple mobile devices (Safari on iOS blocks third-party cookies by default).
• Adjusts cookie and tracking settings within their browser.
• Uses Tor.
• Installs an ad blocker or a similar browser extension.

Avoiding this kind of blocking is one reason to move toward first-party cookies — but it's not the only one.

Benefits of First-Party Cookies

Greater control over collected data. When data is collected under your own domain, you own it outright. There's no ambiguity about data rights, and no intermediary holding the keys to your audience insights.

Longer cookie lifespan. All cookies can be deleted by users manually, but first-party cookies are not automatically swept up by third-party blockers, private browsing modes, or ad blockers. This means they tend to persist longer and provide more durable data continuity.

Branded domains (domain whitelabelling). With a first-party setup, users see your domain — ads.mybrand.com, for example — rather than a generic ad tech company domain like ad.adtechcompany.com. This kind of domain branding is commonly referred to as domain white labelling, and it reinforces brand trust while obscuring the underlying vendor infrastructure.

Together, these advantages allow advertisers to store and make better use of their audience data over time.

How to Implement a First-Party Cookie Approach

Here is a practical step-by-step breakdown for advertisers and marketers looking to adopt this approach.

Step 1: Create a subdomain of your main site. Set up a subdomain such as ads.mybrand.com. This becomes the foundation for collecting first-party data under your own brand.

Step 2: Use a wildcard first-party cookie. Configure a cookie tied to your main domain (e.g., mybrand.com) that is also accessible across subdomains (e.g., ads.mybrand.com). This wildcard structure ensures consistent identification as users move across your properties.

Step 3: Host your ad tech stack under the subdomain. Your ad server, data management platform (DMP), and related infrastructure should sit under ads.mybrand.com. This allows you to serve ads (or at minimum, serve dynamic creatives) and collect audience data directly into your DMP under your own domain. If you're working with third-party vendors — which is the norm for most advertisers — you'll need to point your subdomain's DNS to the vendor's infrastructure. The vendor will also need to make configuration changes on their end to support this setup.

A note on partner site pixels. If you're running tracking pixels on a partner site, those server calls will still be made to ads.mybrand.com, meaning the data is collected under your domain even though a third-party cookie is technically being set from the partner site's perspective. Importantly, the partner site shares data only with you, and their visitors see your branded domain rather than a generic advertising domain.

Limitations: Where Third-Party Cookies Are Still Needed

Switching to a first-party cookie strategy doesn't eliminate every dependency on third-party cookies.

The most common example is retargeting. To run retargeting campaigns across external sites, first-party cookies need to be synced with third-party platforms — DSPs and ad exchanges. This synchronization step reintroduces some reliance on the third-party ecosystem.

That said, the sync process doesn't require sharing the full depth of your audience data. Advertisers can share only what's needed for targeting, keeping granular user interaction data — and the competitive advantage it represents — within their own infrastructure.

A first-party cookie approach won't insulate an advertiser from every tracking limitation in the ecosystem, but it meaningfully reduces exposure to third-party blocking, strengthens data ownership, and positions brands more resiliently as the broader industry continues its gradual shift away from third-party tracking.