What Is a Cookie? | Marketing Dictionary
DICTIONARY · WEB

What is a cookie?

Small pieces of data stored by websites in a user browser.

In plain English

A cookie is a small note a site leaves in the browser so it can recognise something later. It keeps you logged in, remembers your cart, and lets analytics tell a returning visitor from a new one.

Cookies split into first-party, set by the site you are on, and third-party, set by another domain. The second kind is what tracking historically relied on, and it is the kind browsers and regulators have been steadily shutting down.

What to know

First-party versus third-party
First-party cookies are your own and remain fairly reliable. Third-party cookies are widely blocked, which is why cross-site tracking has degraded.
They expire
Session cookies vanish when the browser closes. Persistent ones last until their expiry, though browsers increasingly cap that.
Consent is a legal requirement
In the UK and EU, non-essential cookies need consent before they are set. That includes most analytics and advertising cookies.
They explain analytics gaps
Blocked or cleared cookies mean returning visitors look new and conversions go unattributed. Platform numbers and your own rarely match.

Why it matters

Cookies underpin most of the measurement marketers rely on, and that foundation has been eroding for years. Understanding what still works, mainly first-party data and server-side measurement, is now part of running campaigns you can actually evaluate.

Common mistakes

×Firing tracking cookies before consent is given.
×Treating platform-reported conversions as complete when cookie loss is significant.
×Relying on third-party cookies for audiences and retargeting.
×Using a consent banner that technically asks but sets everything regardless.

FAQs

Are cookies going away?

Third-party cookies are being restricted heavily. First-party cookies remain, which is why first-party data collection matters more each year.

Do I need a cookie banner?

If you set non-essential cookies and serve UK or EU visitors, yes, and it has to actually block them until consent.

WRITTEN BY TARIQ SALLAM
Marketing Consultant. Entrepreneur. Content Creator.

I'm a marketing consultant, entrepreneur and content creator. I help businesses grow through practical marketing, websites, SEO, content and AI.

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