What Are GA4 Parameters? Types List and How to Set Up Custom Parameters
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Authors: Shusaku Yosa
"What exactly are GA4 parameters?" "There are so many types, I can't tell them apart." "I want to set up my own parameters to analyze things in more detail." Understanding parameters is where many people stumble when they start using GA4 (Google Analytics 4).
In GA4, every user action is recorded as an "event," and parameters are what carry the supplementary information about those events. Once you understand parameters and can configure your own as needed, you can visualize user behavior that standard reports don't surface. This article explains GA4 parameters systematically, from the basics through the full list of types, how to set up custom (original) parameters, and the points to watch out for.
A GA4 parameter is a "variable" that represents the supplementary information attached to an event. In GA4, user actions such as page views, clicks, and scrolls are all measured as "events," and parameters play the role of describing how, where, and when that event occurred.
For example, the "page_view" event has parameters attached to it such as page_location (the page URL), which shows which page was viewed, and page_referrer (the referrer URL), which shows where the visitor came from. A single event may have just one parameter, or it may have several.
In the older Universal Analytics (UA), events were measured with a fixed "Category / Action / Label" structure, but GA4 switched to a flexible "event name + parameters" structure. This lets you freely attach whatever information suits your business.
You rarely see the word "parameter" directly on GA4 report screens, but in practice each report displays them under more user-friendly names, and they serve as a crucial foundation for data analysis.
GA4 parameters fall broadly into the following two types by purpose.
It's easier to understand if you frame event parameters as "behavior" and user properties as "attributes." Each of these is further classified by collection method into automatically collected, recommended, and custom.
GA4 events are divided into four types—automatically collected events, enhanced measurement events, recommended events, and custom events—and the parameters attached to each can likewise be organized by collection method. Here we review the types by collection method.
These are parameters collected automatically, with no special configuration, simply by installing GA4. They are immediately useful for grasping basic user behavior. Representative examples include:
These parameters are attached to events you can measure simply by toggling them on or off in the admin screen. They apply to actions such as scrolls, outbound clicks (external link clicks), site search, video engagement, and file downloads. For example, site search collects the search term (search_term), and outbound link clicks collect the destination URL (link_url).
These are parameters with predefined names, tied to events that Google recommends measuring. They are geared toward industry-specific analysis such as e-commerce and gaming, and must be implemented manually. Representative examples include value (amount), currency, and transaction_id attached to the purchase event, as well as item_id and item_name included in the items array. Sending them with their defined names ensures they are aggregated properly in GA4 reports.
These are parameters you define to collect your own company-specific information that automatically collected and recommended parameters can't cover. You can freely set business-specific data such as membership ID, article category, author name, or the color and size of a purchased product. We explain how to set them up in detail in the second half of this article.
To make an original parameter usable in analysis, you need roughly the following two steps. Simply "sending the parameter" is not enough; only by "registering it as a custom definition" can you use it as an analysis dimension in reports.
There are two main ways to send a parameter to GA4: writing it directly in code with gtag.js, and using Google Tag Manager (GTM). For ease of setup and maintainability, GTM is generally recommended.
The basic syntax for sending directly with gtag.js is as follows. You specify the event name and pairs of parameter name and value.
unknown nodeWhen using GTM, select "Google Analytics: GA4 Event" as the tag type, enter the event name, then set the parameter names and values (such as data layer variables) in the event parameters field and publish.
To use a sent parameter in reports, register it as a custom definition in the GA4 admin screen. Create a custom dimension to use it as an analysis axis (a way to segment), or a custom metric to aggregate it as a number.
The steps to register a custom dimension are as follows.
Custom metrics follow the same procedure: from "Create custom metrics," specify the metric name, target parameter, and unit of measurement (standard, currency, time, etc.) and register it. Use custom dimensions for "what you want to classify by" and custom metrics for "what you want to measure as a number."
When setting up a custom dimension, choosing the wrong scope means you won't get the data you intended. GA4's scopes are mainly the following two.
In addition, there is also an "item scope" for handling product-level information for e-commerce sites. Choose user scope for attributes that rarely change, such as membership rank or company size, and event scope for information that changes per action, such as viewed category or selected option.
Custom dimensions and custom metrics have per-property limits. In the free version of GA4, you can set up to 50 event-scoped custom dimensions, 25 user-scoped custom dimensions, and 50 event-scoped custom metrics. Also, the number of parameters you can attach to a single event is, in principle, up to 25; if you exceed this, you need to split the event. When you reach a limit, you can archive unnecessary ones to create new ones.
It's important to keep parameter names consistent. Deciding on a unified rule using half-width alphanumerics and underscores—such as user_id or product_id—makes later data organization and analysis easier.
Even after you set up a custom dimension, data may not be reflected for roughly the first 48 hours, and it may display as "(not set)" in reports. Even if no value appears right after setup, wait a while before checking.
Sending personally identifiable information (PII) such as names, email addresses, or phone numbers as parameters is prohibited by Google's policies. Comply with your privacy policy, obtain user consent as needed, and design your setup so it doesn't include personal information.
Setting up too many parameters makes the data complex and harder to analyze. First check whether standard dimensions can handle it, and set up only what you truly need by working backward from your business goals—that is the key to successful operation.
GA4 parameters are variables representing the supplementary information attached to events. They are broadly divided into "event parameters (behavior)" and "user properties (attributes)," and split by collection method into automatically collected, recommended, and custom. Information that standard parameters can't capture can be collected by setting up original (custom) parameters.
Original parameters become usable as analysis axes once you send them via gtag.js or GTM and register them as custom definitions in the GA4 admin screen. While paying attention to scope selection, setup limits, handling of personal information, and the time it takes for data to appear, design the parameters that directly serve your own analysis goals in a planned way. Master parameters, and the resolution of your user-behavior analysis will rise significantly, leading to more precise improvement measures.
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