When you track a purchase event, what information do you capture? Just that a purchase happened? Or do you capture the amount, the product category, the coupon code, the user ID? Event parameters and custom properties let you attach data to events. A purchase event with just "purchase happened" tells you volume. A purchase event with amount, category, and coupon tells you what's profitable. Parameters transform events from simple counters to rich business signals.
This article explains how to set up event parameters and custom properties to capture the details that matter.
What Are Event Parameters and Custom Properties
An event parameter is a piece of information attached to an event. When someone makes a purchase, you attach the purchase amount as a parameter. When someone submits a form, you attach the form name as a parameter.
Custom properties are attributes about the visitor or page. The visitor's subscription level. The page category. The traffic source. Properties provide context for understanding events.
Parameters and properties transform events from "something happened" to "something happened with this context and these details." The difference is enormous. A purchase event tells you sales volume. A purchase event with amount, category, and coupon tells you what type of sales are profitable.
Identify Important Parameters
Before you start capturing parameters, identify which ones matter. For a purchase event, what matters? Amount. Product category. Coupon code used. Device type. Traffic source. All of these provide insight into your sales.
Don't capture everything. That creates noise. Capture parameters that influence business decisions. If you don't care about the color of the product, don't capture it.
Document why each parameter matters. "Purchase amount tells us average order value." "Product category tells us which products sell best." This documentation helps teams understand the tracking system.
Set Up Purchase Event Parameters
For a purchase event, capture amount, currency, product category, and coupon code. These parameters answer key business questions.
In your tag manager, configure the purchase tag to capture these values from your data layer. The data layer provides purchase_amount. The tag captures it as the "value" parameter. The data layer provides product_category. The tag captures it as the "category" parameter.
Test parameter capture. Make a test purchase. Check real-time reports. Did the parameters appear? Did they have correct values?
Set Up Form Event Parameters
For a form submission event, capture the form name, form type, and whether submission was successful. These parameters show which forms drive conversions.
In your data layer, populate formName, formType, and submissionSuccess when a form submits. Your tag reads these values and attaches them to the event.
Form parameters help you compare form performance. Newsletter signup forms convert differently than demo request forms. Parameters let you see the difference.
Use Custom Properties for Visitor Context
Custom properties provide context about visitors. Subscription level. Account age. Geographic location. Traffic source. These properties help you understand who converts and who doesn't.
Set custom properties when the visitor arrives. Update them as their status changes. A visitor becomes a customer. Update their subscription_level property from "free_trial" to "paid."
Use properties in segments and audiences. Create a segment of paid subscribers. Create a segment of visitors from Google Ads. Compare how they behave.
Manage Parameter Names Consistently
Use consistent naming for parameters across all events. If one event uses "product_category," don't use "category" in another event. Consistency makes analysis easier.
Define a parameter naming standard. All lowercase with underscores. Descriptive names. "product_category" instead of "cat." "purchase_amount" instead of "amt." Good naming prevents confusion.
Document all parameters in your event registry. For each event, list the parameters. Document what each parameter means. Documentation helps teams use parameters correctly.
Test Parameter Values
Test that parameters capture correct values. Make a test purchase with specific values. Check the event in real-time. Do the parameters match? If purchase amount is $49.99, does the value parameter show 49.99?
Test with different values. A purchase for $9.99. A purchase for $999.99. Different currency codes. Different product categories. Verify parameters work with various values.
Compare parameter values to your backend. If your backend says the purchase was $49.99, the event parameter should say $49.99. Mismatches indicate a problem.
Frequently asked questions
How many parameters should each event have?
Five to ten is typical. More is possible but harder to manage. Every parameter adds complexity. Include parameters that answer business questions. Leave out parameters that don't. With WEMASY's website builder, you can set this up directly on your website.
Should we capture personally identifiable information as parameters?
Be careful. Customer names, email addresses, and phone numbers in event parameters can create privacy issues. Use user IDs instead. Capture only the information you absolutely need for analysis.
Can we capture parameters that don't exist on every instance of an event?
Yes. If a purchase sometimes has a coupon and sometimes doesn't, capture it when it exists. Leave it empty when it doesn't. Most platforms handle optional parameters fine.
How do we ensure parameter values are consistent?
Document expected values. For product_category, list valid values. "Electronics," "Clothing," "Home Goods." Enforce these values. Tags should only capture valid values.
Do parameter names need to match across different analytics platforms?
No. Google Analytics parameters don't need to match Facebook parameters. Each platform has different parameter naming. But internally, within each platform, use consistent names.
Can we update parameters after an event fires?
No. Parameters are attached when the event fires. You can't go back and add parameters later. Get the parameters right before the event fires.