A small piece of data stored in a web browser by a website, used to remember information about a visitor — login state, preferences, or browsing behavior for tracking and advertising purposes.
Why it matters
Cookies have historically been foundational to digital advertising's ability to track users across sites and measure ad performance — but third-party cookies specifically are being phased out or restricted by major browsers and regulations, reshaping how tracking and attribution work industry-wide.
In a sentence
"With third-party cookies being phased out, a lot of our retargeting strategy has had to shift toward first-party data and alternative identifiers."
Related terms
- Often confused with: Pixel (a cookie is data stored in the browser; a pixel is a small snippet of code embedded on a page that triggers a tracking event, which may or may not involve setting a cookie).