Cookies are small text files stored on a user's browser when they visit a website. They allow the website - and third-party services embedded within it - to remember information about the user between sessions: their login status, cart contents, language preferences, and browsing behavior. For e-commerce and digital advertising, cookies have historically been the primary mechanism for user identification, behavioral tracking, and ad targeting across the web.
There are two types of cookies with distinct roles. First-party cookies are set by the website the user is visiting. They are used for core site functionality - keeping items in a cart, maintaining a logged-in session, remembering preferences - and for analytics tools like Google Analytics that measure on-site behavior. First-party cookies are generally not subject to the same restrictions as third-party cookies. Third-party cookies are set by external domains embedded in a page - advertising networks, social media pixels, analytics services. They enable cross-site tracking: a cookie set by Meta's pixel on one website can identify the same user on another website, enabling retargeting across the web and building cross-site behavioral profiles for ad targeting.
Third-party cookies have been curtailed, though not in the way the industry spent years preparing for. Safari and Firefox have blocked them by default since long before the debate went mainstream, and Apple's App Tracking Transparency (ATT) framework extended similar restrictions to mobile app tracking. Google's plan to deprecate them in Chrome was abandoned, so they still function in the browser that carries most ecommerce traffic. These changes have significantly reduced the signal available for tracking pixel-based advertising and have been a primary driver of the shift toward first-party data and zero-party data collection as the foundation of personalization and audience targeting.
Start with what did not happen: Google abandoned third-party cookie deprecation in Chrome, and those cookies still function there. Signal loss arrived anyway, through Safari and Firefox blocking by default, app tracking restrictions on mobile, and consent gating. Planning around a Chrome shutoff date is planning for an event that was called off. Planning around thinner data is not.
The cost lands in two places. Smaller matchable audiences and weaker conversion signal mean the ad platforms optimize on less, so the same budget buys less well-matched traffic and acquisition cost drifts up with nothing on the site having changed. And under-reported conversions make working channels look like losing ones, which tempts brands to cut spend that was paying. The responses that hold are owning identity — email, SMS, accounts, order history — and judging spend on blended numbers rather than platform-reported ones.
The common mistake is treating this as an advertising problem when it lands first on measurement. A consent banner that blocks analytics until a shopper opts in creates a step change in reported sessions and conversions that looks like a traffic collapse and is not one, so record the date the banner shipped and read every trend against it. Handle both sides deliberately: consent and data compliance work at collection, and e-commerce data and analytics at reporting.
Owning identity through email, SMS, and account data only works if the collection points are actually built into the store rather than left to whatever a marketing tool happens to capture, which is the practical setup covered in first-party data collection on Shopify.
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