GA4 Parameter Validator

Why GA4 Parameter Validation Prevents Silent Data Loss

GA4 does not throw errors when you send invalid parameters — it silently drops them. A parameter name that is too long, uses a reserved prefix, or contains an illegal character simply disappears from your GA4 reports with no warning in the UI or debug console. This silent failure mode is one of the most common causes of missing dimensions in GA4 and incomplete data in Google Ads enhanced conversions. The GA4 parameter validator catches these issues before your code ships, eliminating data gaps at the source.

GA4 Parameter Rules Every Developer Must Know

Google's GA4 parameter specification imposes strict constraints that are easy to violate — especially when migrating from Universal Analytics or building a data layer for the first time:

• Name length limit: 40 characters. Parameter names longer than 40 characters are silently truncated or dropped. This is a common issue when migrating verbose UA custom dimensions.
• Value length limit: 100 characters. String values exceeding 100 characters are truncated at exactly 100 characters. Numeric values have no practical limit.
• Reserved prefixes. Any parameter name starting with firebase_, google_, or ga_ is reserved by Google and will be ignored. Parameters like ga_session_id and firebase_conversion cannot be overridden.
• Allowed characters. Parameter names can only contain letters (a–z, A–Z), numbers (0–9), and underscores. No hyphens, spaces, periods, or special characters.
• 25 custom parameter limit per event. Standard ecommerce parameters (currency, value, items) do not count toward this limit, but all other custom parameters do.

When to Use Numeric vs String Parameters in GA4

GA4 supports three value types — string, number (integer or float), and boolean. The type you send determines what you can do with the data in GA4 reports and Google Ads:

• Numeric parameters (e.g., value, quantity, discount) can be used to create calculated metrics in GA4, aggregated in revenue reports, and imported into Google Ads for Smart Bidding signals. Always send revenue and quantity fields as numbers, not strings.
• String parameters (e.g., item_category, promo_name) appear as dimensions in GA4 Explorations and custom reports. They cannot be summed or averaged.
• Boolean parameters are treated as strings ("true"/"false") in GA4 reports. For numeric flags, use 0 and 1 instead — they can then be summed to count occurrences.

Sending a revenue value as a string ("49.99" instead of 49.99) is a common mistake that breaks purchase attribution, revenue reporting, and ROAS calculations across both GA4 and Google Ads. This validator checks the type of every value you send and flags potential mismatches.