Published on 2025-06-28T03:37:43Z

What is a Session Token? Examples in Plainsignal and GA4

Session Tokens are unique identifiers assigned to each visitor session on a website or app. They enable analytics platforms to group user interactions—such as pageviews, events, and transactions—into coherent sessions. A session token typically resets after a period of inactivity (often 30 minutes) or when a user closes the browser, ensuring that metrics like session duration, bounce rate, and pages per session are calculated accurately. While traditional analytics solutions use cookies to store session tokens, modern privacy-focused tools like Plainsignal can generate cookie-free session tokens via in-memory mechanisms, reducing reliance on trackers. In Google Analytics 4 (GA4), the session token is represented by the session_id parameter and is tied to the _ga cookie by default. By understanding how session tokens work, you can configure and interpret session-based metrics more reliably across different analytics products.

Illustration of Session token
Illustration of Session token

Session token

A session token uniquely groups user interactions into coherent sessions for accurate analytics in tools such as Plainsignal and GA4.

Why Session Tokens Matter

Session tokens form the backbone of session-based metrics by grouping user interactions into distinct visits. They prevent fragmentation of data when users reload pages or navigate within the site, ensuring accurate calculation of session duration, bounce rate, and pages per session. Different implementations—cookie-based or cookie-free—can affect privacy, performance, and compliance. Tools like PlainSignal leverage in-memory tokens to minimize reliance on cookies, while GA4 uses a combination of cookies and parameters. Understanding their impact helps analysts interpret data consistently across platforms.

  • Accurate sessionization

    Session tokens ensure events are grouped correctly into sessions, preventing data fragmentation when users navigate between pages or reload without a new session starting.

    • Timeout thresholds:

      Defines the inactivity window (e.g., 30 minutes) before a session token expires and a new session starts.

    • Session boundary logic:

      Rules that determine when a session ends, such as crossing midnight or changing campaign parameters.

  • Reliable bounce rate calculation

    By assigning a unique token per session, bounce rates are calculated based on single-session interactions, improving data accuracy.

  • Privacy compliance

    Cookie-free session tokens, like those used by PlainSignal, help meet privacy regulations by minimizing persistent identifiers.

    • In-memory tracking:

      Session tokens are generated at runtime and stored temporarily, reducing persistent data storage.

    • No third-party cookies:

      Eliminates reliance on third-party cookies, enhancing user privacy and reducing ad tracking.

How Session Tokens Work

Session tokens are generated, stored, and transmitted by analytics libraries or servers to maintain context across user interactions. They must be both unique and secure to prevent collisions or tampering. Storage methods vary—cookies, localStorage, or in-memory—and determine token persistence and privacy characteristics. Expiration rules define when a session ends and a new one begins, directly impacting session-based metrics. Understanding these mechanics helps optimize configuration and reduce tracking errors.

  • Token generation

    Analytics SDKs or servers generate a random, unique token when a user starts a session. Good tokens have high entropy to avoid collisions.

    • Randomness and uniqueness:

      High entropy ensures tokens are unique across millions of sessions, preventing overlap.

    • Client vs. server generation:

      Tokens can be created client-side (e.g., with JavaScript) or server-side, affecting security and control.

  • Token storage and transmission

    Tokens can be stored in cookies, localStorage, or in-memory. They must accompany each event payload back to the analytics endpoint.

    • Cookie storage:

      Uses HTTP-only or same-site cookies for persistence and security.

    • In-memory storage:

      Stored temporarily in JavaScript memory, discarded on page close.

    • Http headers or query params:

      Tokens can be sent via custom headers or URL parameters in API calls.

  • Expiration and renewal

    Session tokens expire after a set idle period or on browser close. Renewing tokens starts a new session.

    • Idle timeout:

      Standard timeout is 30 minutes of inactivity, but configurable per implementation.

    • Manual session control:

      Tools like GA4 allow overriding session boundaries with parameters like session_start or session_end events.

Implementation Examples

Practical examples illustrate how session tokens are implemented in different analytics platforms. Below are snippets for PlainSignal’s cookie-free tracking and GA4’s standard setup. Customize IDs and domains according to your configuration.

  • Plainsignal

    PlainSignal uses a cookie-free, in-memory session token that is generated on page load and sent with each event.

    • 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>

  • Google analytics 4

    GA4 generates a session token stored in the _ga cookie and includes session_id in event payloads.

    • Setup snippet: 
      <script async src="https://www.googletagmanager.com/gtag/js?id=G-XXXXX"></script>
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());
  gtag('config', 'G-XXXXX');
</script>

Best Practices

Adhering to best practices ensures session tokens remain reliable, secure, and privacy-compliant. Regular review and configuration can prevent tracking errors and support accurate analytics.

  • Use secure storage

    Store tokens in secure, same-site cookies or in-memory, and avoid exposing them in URLs.

    • Httponly and secure flags:

      Ensure cookies have HttpOnly and Secure attributes to prevent access via JavaScript and mandate HTTPS.

  • Respect user consent

    Only generate and send session tokens after obtaining consent, in compliance with GDPR and CCPA.

  • Monitor session metrics

    Regularly audit session durations, bounce rates, and token collisions to ensure data quality.

    • Alert thresholds:

      Set alerts for abnormal session lengths or counts that may indicate tracking issues.

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