Published on 2025-06-27T23:57:06Z

What Is an Event Parameter? Examples in GA4 and PlainSignal

An Event Parameter is a key–value pair that enriches analytics events with additional context. In analytics platforms, events represent user interactions—like button clicks, form submissions, or page views—and parameters provide details such as categories, labels, or values. For example, when tracking a purchase event, parameters might include transaction_id, value, and currency. In Google Analytics 4 (GA4), event parameters drive custom reports, audiences, and predictive metrics. PlainSignal, a privacy-focused, cookie-free analytics solution, also supports event parameters through a minimal JavaScript API. By structuring your event parameters thoughtfully, you can unlock deeper insights into user behavior across both GA4 and PlainSignal.

Illustration of Event parameter
Illustration of Event parameter

Event parameter

Key–value pairs that add context to analytics events, enabling richer insights in GA4 and PlainSignal.

Understanding Event Parameters

Event parameters are metadata attached to analytics events, expressed as key–value pairs. They allow you to specify attributes such as categories, labels, values, or user properties that enrich raw event data. Parameters help answer questions like “Which product was viewed?”, “How much did the user spend?”, or “What user role triggered this action?”. By tagging events with parameters, analysts can segment audiences, filter reports, and build custom metrics. Understanding their structure and purpose is foundational for effective event-based analytics.

  • Definition

    An event parameter is a key–value pair sent alongside an analytics event to provide extra context. The key identifies the parameter name (e.g., page_type), and the value supplies the detail (e.g., landing).

  • Structure and components

    Keys are alphanumeric strings (often lowercase with underscores) that represent the parameter name, while values can be strings, numbers, or booleans. Most platforms enforce naming rules (e.g., GA4 keys must be under 40 characters and contain only letters, numbers, or underscores) and value-type constraints.

Implementing Event Parameters in GA4

Google Analytics 4 uses event parameters extensively to power analysis, audiences, and machine-learning insights. You define parameters when you log an event, and they become available for custom reporting and segmentation once registered in the GA4 interface.

  • Defining parameters with gtag.js

    With the gtag.js library, you attach parameters directly in the event command. For example:

    gtag('event', 'purchase', {
  transaction_id: 'T1234',
  value: 19.99,
  currency: 'USD'
});

  • Parameter limits in ga4

    GA4 allows up to 25 event parameters per event, with a maximum key length of 40 characters and up to 100 bytes per value. Exceeding these limits will result in dropped parameters.

Implementing Event Parameters in PlainSignal

PlainSignal provides a lightweight, cookie-free API for tracking events with parameters. You include their minimal script on your page, then call the global function to send events along with any number of custom parameters.

  • Including the plainsignal snippet

    First, add the PlainSignal script to your page:

    <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>

  • Sending events with parameters

    After loading the script, use the global PlainSignal function to send events:

    <script>
  PlainSignal('event', 'signup', {
    user_role: 'member',
    source: 'newsletter'
  });
</script>

Best Practices for Event Parameters

Adhering to best practices ensures consistency, data quality, and scalability. Clear parameter definitions help teams across engineering, analytics, and marketing collaborate effectively.

  • Consistent naming conventions

    Use lowercase letters and underscores; avoid spaces or special characters. For example, prefer product_id over Product ID or product-id.

  • Limit parameter usage

    Only include parameters that drive analysis or reporting value. GA4 supports 25 parameters per event; PlainSignal may impose its own limits—check documentation.

  • Validate parameter values

    Ensure values match expected data types and formats (e.g., ISO currency codes, numeric values) to avoid downstream reporting errors.

Common Use Cases

Event parameters power a variety of analytics scenarios, from e-commerce tracking to feature usage analysis and marketing attribution.

  • E-commerce tracking

    Capture product IDs, prices, quantities, and categories as parameters on events like add_to_cart, purchase, and view_item to analyze sales performance.

  • Feature usage analysis

    Track button clicks, form submissions, and video plays with detailed parameters (e.g., button_name, form_id, video_duration) for deep engagement insights.

  • Marketing attribution

    Pass campaign IDs, sources, and mediums as event parameters to attribute conversions and user actions back to specific marketing efforts.

Related terms