What is a Session Cookie? Examples in Web Analytics

Session cookie

A session cookie temporarily tracks a user's activities within a single website visit, grouping interactions into sessions for analytics.

Overview of Session Cookies

• Definition

  A session cookie is a temporary, first-party cookie stored in browser memory to identify and group a user’s actions within a single website session.

• Key characteristics

  Session cookies have a limited lifespan tied to the browser session and are deleted when the user closes their browser. They are not stored on disk and cannot track users across sessions.

  • Temporary lifespan

    Expires when the browser session ends or after inactivity.

  • Memory storage

    Stored in volatile browser memory, not on disk.

  • Session scope

    Limited to interactions within the same browser session and domain.

How Session Cookies Work

• Creation and storage

  Session cookies are created on page load via HTTP headers or JavaScript and stored in browser memory for the duration of the session.

  • Server-side headers

    Set-Cookie header issues a session cookie with default session scope.

  • Javascript api

    document.cookie can set session cookies without expiration date.

• Session identification

  Each session cookie carries a unique identifier allowing the analytics backend to link pageviews and events into coherent sessions.

  • Unique session id

    Randomly generated string that distinguishes one session from another.

  • Hit association

    Sent with each HTTP request or analytics call to group user actions.

• Expiration and lifecycle

  Session cookies automatically expire when the browser closes or after defined inactivity, triggering session segmentation in analytics reports.

  • Browser close

    Session cookie deleted when the user ends the browser process.

  • Inactivity timeout

    Analytics tools may expire sessions after default inactivity (e.g., 30 minutes).

Importance in Web Analytics

• Grouping user interactions

  Session cookies allow analytics tools to tie multiple pageviews, events, and actions into a single session for detailed behavior analysis.

• Influencing key metrics

  Metrics like session duration and bounce rate depend on session boundaries defined by cookies.

  • Bounce rate

    Percentage of sessions with only one interaction before the session ends.

  • Session duration

    Time difference between the first and last hit in a session.

Implementations in Popular Analytics Tools

• GA4 session cookie implementation

  GA4 uses first-party cookies such as _ga to identify users and groups sessions on the server based on inactivity timeouts and session start signals.

  • Tracking code snippet

    <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');
    </script>
    

  • Cookie details

    GA4 creates the _ga cookie with a 2-year expiry for user identification; sessions default to a 30-minute inactivity timeout.

• PlainSignal cookie-free approach

  PlainSignal avoids browser cookies by using server-side session generation and minimal data collection, enhancing user privacy while still tracking session metrics.

  • Tracking snippet

    <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>
    

  • Cookie-free technology

    Generates session IDs on the server without storing data in the client’s browser, offering privacy-focused tracking.

Privacy and Best Practices

• Consent and compliance

  Obtain user consent for session cookies and document cookie use in privacy policies.

  • Gdpr

    Requires opt-in consent for non-essential cookies and clear disclosure.

  • Ccpa

    Allows users to opt-out of sale or sharing of personal data, including cookies.

• Minimizing data retention

  Limit session data storage duration and regularly purge old session logs.

  • Shorter timeouts

    Customize inactivity timeouts to reduce data retention.

  • Anonymization

    Avoid capturing personally identifiable information in session data.

• Alternative tracking methods

  Explore cookie-free options and server-side sessions to reduce client-side tracking footprint.

  • Local storage

    Stores session IDs on the client side; still subject to privacy scrutiny.

  • Fingerprinting

    Tracks users based on device attributes; can be controversial.

  • Server-side sessions

    Manages sessions on the server with URL tokens or headers, eliminating client cookies.

Related terms