Published on 2025-06-28T03:49:09Z

What are Cookies in Analytics? Examples and Usage

Cookies are small text files stored in a user’s browser that hold key–value data for identifying and tracking user interactions. In analytics, cookies assign unique identifiers to visitors, enabling tools to distinguish between new and returning users, measure sessions, and track engagement across pages. They can persist data like user preferences, consent status, and attribution parameters. However, cookies also raise privacy concerns and are subject to regulations like GDPR and CCPA. As browsers phase out third-party cookies and users demand greater privacy, analytics teams must balance data accuracy with compliance and explore cookie-free alternatives.

Illustration of Cookies
Illustration of Cookies

Cookies

Cookies are small browser files that store identifiers to track user sessions and behavior in analytics, with privacy and compliance considerations.

Overview of Cookies in Analytics

Cookies are small text files that store key–value pairs in a browser. In web analytics, they assign unique IDs to visitors, track sessions, and record pageviews. By persisting identifiers, cookies enable analytics tools to build user journeys, measure engagement, and attribute conversions. While invaluable for insights, cookies face challenges from privacy regulations and browser restrictions, making alternative tracking methods increasingly relevant.

  • Definition

    In analytics, a cookie is a small piece of data stored on the client side that assigns a unique ID to a user’s browser.

  • Purpose in analytics

    Cookies help identify users, track sessions, measure engagement, and attribute conversions across web pages and visits.

How Cookies Work

Cookies operate via HTTP headers or JavaScript and travel with each matching request, enabling stateful interactions in stateless HTTP. They have defined scopes (domain, path) and lifespans (session or persistent). Understanding these mechanics is crucial for correct implementation and regulatory compliance.

  • Cookie creation

    Cookies can be set using the Set-Cookie HTTP response header or via JavaScript (document.cookie). Once set, browsers include cookies in subsequent requests matching the defined scope.

    • Http headers:

      Server responses include Set-Cookie headers specifying name, value, domain, path, expiry, and security flags.

    • Client-side scripting:

      Scripts use document.cookie = 'name=value; expires=...; path=...'; to create or modify cookies dynamically.

  • Scope and lifespan

    The domain and path attributes determine which pages send the cookie. The expires or max-age attribute defines persistence, distinguishing session cookies from persistent cookies.

    • Session cookies:

      Deleted when the browser session ends.

    • Persistent cookies:

      Remain until a set expiration date or user clears them.

Types of Cookies

Cookies vary by duration, purpose, and security. Common categories include session vs persistent, secure vs HttpOnly, and SameSite settings. Each type has implications for data integrity, user experience, and privacy compliance.

  • Session cookies

    Temporary cookies that last only for the duration of a browser session.

  • Persistent cookies

    Cookies that remain on users’ devices until they expire or are manually deleted.

  • Secure and httponly

    Secure cookies require HTTPS; HttpOnly cookies are inaccessible to JavaScript, reducing XSS risk.

  • Samesite attribute

    Controls cross-site cookie sending: Strict, Lax, or None (for third-party).

Cookies in Analytics Tools

Different analytics platforms implement cookies in unique ways. Comparing traditional cookie-based analytics like GA4 with modern cookie-free solutions highlights the trade-offs between data richness and privacy.

  • Google analytics 4 (ga4)

    GA4 uses first-party cookies (_ga, _gid, _gat) to identify users and throttle requests. Cookies persist identifiers, session state, and user properties.

    • _ga:

      Stores the client identifier, expires after 2 years.

    • _gid:

      Distinguishes users, expires after 24 hours.

    • _gat:

      Used to throttle request rate.

  • Plainsignal: cookie-free tracking

    PlainSignal provides privacy-first analytics without cookies by using lightweight event-based tracking and server-side processing. It avoids storing user identifiers in the browser, reducing privacy risks while delivering core metrics.

Implementation Example

Below are typical snippets for integrating cookie-based and cookie-free analytics on a webpage.

  • Ga4 tracking code

    <!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=GA_MEASUREMENT_ID"></script>
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());
  gtag('config', 'GA_MEASUREMENT_ID');
</script>

  • Plainsignal tracking code

    <link rel="preconnect" href="//eu.plainsignal.com/" crossorigin />
<script defer data-do="yourwebsitedomain.com" data-id="0GQV1xmtzQQ" data-api="//eu.plainsignal.com" src="//cdn.plainsignal.com/PlainSignal-min.js"></script>

Privacy and Compliance

Implementing cookies requires adherence to global privacy regulations. Analytics teams must manage user consent, data retention, and transparency to mitigate legal risks and maintain trust.

  • Gdpr

    Enforces consent for storing non-essential cookies in the EU. Requires clear notices and opt-in before setting analytics cookies.

  • Ccpa

    Gives California residents rights to opt out of sale of personal data and request deletion of stored cookies deemed personal information.

  • Consent management platforms

    Tools like OneTrust or Cookiebot help display banners, record user choices, and block unauthorized cookies until consent is granted.

Best Practices

Adopting best practices ensures reliable data collection while respecting user privacy and evolving browser policies.

  • Minimize cookie lifespan

    Set appropriate expiration to balance analytics needs with privacy. Prefer session cookies when possible.

  • Implement opt-out mechanisms

    Provide clear options for users to opt out of analytics tracking, even for first-party cookies.

  • Maintain transparency

    Publish a clear cookie policy detailing usage, purpose, and data retention for analytics cookies.

Future of Cookies in Analytics

Privacy-driven technology trends are reshaping analytics. Professionals must adapt by exploring new measurement and attribution methods that don’t rely on traditional cookies.

  • Third-party cookie deprecation

    Major browsers are phasing out third-party cookies, impacting cross-site tracking and remarketing capabilities.

  • Alternative tracking methods

    Server-side tagging, first-party data strategies, and cookie-free tools (e.g., PlainSignal) provide privacy-safe analytics.

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