Third-Party Cookie
A third-party cookie is a tracking file set by a domain other than the site being visited, historically used to follow people across the web.
What it actually means
When a site you visit loads content from another company — an ad network, a social widget — that company could historically drop its own cookie and recognize you again on every other site carrying its code. Third-party cookies powered cross-site retargeting and attribution for two decades. That era is ending: Safari and Firefox block them outright, and regulation restricts them everywhere. Their decline is the root cause behind shrinking retargeting audiences, blind spots in attribution, and the industry-wide shift toward first-party data, server-side tracking, and modeled measurement. Understanding this one term explains most of why digital tracking got harder after 2020.
The practical takeaway for a local business: rented tracking is dying, so the customer list you own — emails, phone numbers, booking history — is now your most durable marketing asset.
Related terms
First-party data is information you collect directly from your own customers and prospects, such as email addresses, phone numbers, and purchase history.
iOS 14's App Tracking Transparency requires apps to ask users for permission before tracking them, which sharply reduced the data Meta can use for ad targeting and measurement.
Consent mode adjusts how tracking tags behave based on a visitor's cookie-consent choice, using modeled data to fill gaps when tracking is declined.
The Meta Pixel is a snippet of code on your website that tracks visitor actions and sends them back to Meta for measurement and ad optimization.
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