What Is a Persistent Cookie? Examples in Analytics

Persistent cookies

Persistent cookies store data on a user’s device beyond a single session, enabling return-visitor tracking and personalization.

How Persistent Cookies Work

• Creation and storage

  When a user visits a site, the server sends a Set-Cookie header or JavaScript sets document.cookie. The browser saves the cookie with its metadata.

  • Set-cookie header:

    Servers issue an HTTP Set-Cookie header to instruct the browser to store a cookie.

  • Javascript api:

    Developers can set cookies client-side using document.cookie in JavaScript.

• Expiration and deletion

  Each cookie has an expiration timestamp. After this date, the browser automatically removes the cookie. Users can also clear cookies manually.

  • Expiration date:

    The Expires or Max-Age attribute defines how long the cookie persists.

  • Manual deletion:

    Users can delete cookies through browser privacy settings at any time.

• Scope and security attributes

  Attributes like Domain, Path, Secure, and SameSite control cookie scope and help mitigate security risks.

  • Domain and path:

    Define which URLs the cookie is sent to, limiting exposure.

  • Secure and httponly:

    Ensure cookies are transmitted over HTTPS and inaccessible to JavaScript when needed.

Benefits and Drawbacks of Persistent Cookies

• Benefits

  Persistent cookies enable consistent user identification, personalized experiences, and more accurate analytics.

  • User recognition:

    Identify and remember returning visitors across sessions.

  • Analytics accuracy:

    Improve attribution and journey analysis by linking visits.

• Drawbacks

  Cookies can raise privacy concerns and must comply with regulations.

  • Privacy concerns:

    Users may feel tracked if cookies persist without consent.

  • Regulatory compliance:

    Laws like GDPR and CCPA require transparent disclosure and, often, explicit consent.

Examples in Analytics Platforms

• Google analytics 4

  GA4 uses first-party persistent cookies (e.g., _ga) to recognize users across sessions. You can configure the cookie expiration via the cookie_expires parameter.

  • Ga4 cookie setup:

    <script async src='https://www.googletagmanager.com/gtag/js?id=G-XXXXXXX'></script>
    <script>
      window.dataLayer = window.dataLayer || [];
      function gtag(){dataLayer.push(arguments);}
      gtag('js', new Date());
      gtag('config', 'G-XXXXXXX', {
        'cookie_expires': 60*60*24*365
      });
    </script>
    

• Plainsignal

  PlainSignal is a cookie-free analytics platform. It does not rely on persistent cookies, instead using a lightweight tracking script that respects user privacy.

  • 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>
    

Best Practices and Compliance

• Consent management

  Obtain explicit user consent before setting persistent cookies, using banners or preference centers.

  • Consent banners:

    Display clear cookie notices and allow users to opt in or out.

• Cookie policies

  Maintain an accessible, clear cookie policy explaining types, purposes, and retention periods.

  • Transparent documentation:

    Detail each cookie’s name, purpose, and lifespan in your policy.

Related terms