Third-Party Cookies
Cookies created by a domain different from the one being viewed (like Facebook, Google, or advertisers). Enable cross-site tracking. Blocked in Safari and Firefox, and gradually in Chrome. A shift affecting the entire ad industry.
In practice
Third-party cookies are fading away. Safari blocked them in 2017. Firefox in 2019. Chrome announced deprecation (repeatedly delayed to 2025+). Any retargeting, remarketing, or cross-site tracking based on them will work less well. Those preparing now with a first-party strategy gain a competitive edge.
Common misconception
'Third-party cookies disappearing means the end of advertising.' No. Meta Conversions API, Google Enhanced Conversions, and server-side tracking replace third-party cookies with platform-level matching. Advertising continues — just differently and less transparently.
How to fix it
Preparing for third-party cookie deprecation? (1) Move to server-side tracking (Conversions API), (2) build first-party data — email lists, CRM, account creation, (3) contextual targeting — advertise based on page content rather than user profile, (4) clean rooms (advanced) — Meta / Google Clean Room.
Example
D2C store: 60% of retargeting relied on third-party cookies. Safari users: already invisible. Preparation: (1) Meta Conversions API, (2) email-based retargeting (Customer Match), (3) first-party segments. 18 months later: Meta ROAS fell 8% (from 4.1 to 3.8) — far less than expected.
Priority
Third-party deprecation is already well underway in Safari/Firefox. Start preparing now: (1) Conversions API, (2) email collection, (3) a first-party data strategy. A store that waits will be caught off guard.
Related terms
Keep learning. Metrics that touch the same area:
- API – Application Programming InterfaceTechA 'language' for communication between systems. A store connects via API to shipping providers, Klaviyo, and payment platforms. The API is the 'pipe' through which data flows.
- Headless CommerceTechAn architecture that separates the front end (what the customer sees) from the back end (catalog, payments, inventory). Gives full freedom in design and channel integration.
- CRM – Customer Relationship ManagementTechA system for storing customer data, communication history, and purchase history. Enables segmentation, personalization, service tracking, and lifecycle management. HubSpot, Salesforce, Klaviyo.
- CDP – Customer Data PlatformTechConsolidates customer data from multiple sources into a unified real-time profile. More advanced than a CRM — pulls behavioral events and enables instant segmentation.
- Marketing AutomationTechSystems that trigger automatic marketing actions: cart abandonment → email, purchase → thank-you SMS, 90 days without a purchase → win-back campaign.
- PWA – Progressive Web AppTechA website that behaves like an app — fast, works offline, and can be added to the home screen. Cuts load time by 50%+ and increases engagement and CR on mobile.
Jimmy tracks your Third-Party Cookies, automatically
WhatsApp alerts when something important changes. No dashboards, no hassle.