GA4 event naming rules
GA4 silently drops or rejects events that break its rules, and you usually find out weeks later when a report is empty. These are the rules this tool checks:
| Rule | Limit |
|---|---|
| Event and parameter name length | 40 characters |
| Allowed characters | Letters, numbers and underscores; must start with a letter |
| Case | Case-sensitive: Sign_Up and sign_up are different events |
| Reserved prefixes | firebase_, google_, ga_ (parameters also _ and gtag.) |
| Reserved event names | e.g. session_start, first_visit, user_engagement, error |
| Parameters per event | 25 |
| Parameter value length | 100 characters (standard property) |
Use recommended events where they fit
Before inventing a name, check whether Google already has one. Recommended events such as generate_lead, sign_up, purchase and add_to_cart feed GA4's built-in reports and Google Ads conversion suggestions. A custom quote_form_submit event works, but generate_lead with a form_name parameter works better. This tool suggests the recommended event when your description matches one.
A naming convention that scales
- Lowercase snake_case, always. One casing rule removes a whole class of duplicate events.
- Object then action:
video_play,pricing_view,calculator_submit. Related events then sort together in reports. - Put detail in parameters, not names. One
cta_clickevent with acta_textparameter beats twenty events likehero_button_click. - Don't re-send what GA4 already collects. Enhanced Measurement already sends
page_view,scroll, outboundclick,file_downloadand form events. - Never send personal data. Emails, phone numbers and names in parameters break Google's terms.
From event name to GA4 report
Push the event to the dataLayer with the code above, create a Custom Event trigger and a GA4 Event tag in Google Tag Manager, then register each parameter you want to report on as a custom dimension in GA4 (Admin → Custom definitions). Parameters that aren't registered are collected but don't appear in standard reports.
Frequently asked questions
What are the rules for GA4 event names?
GA4 event names must be 40 characters or fewer, start with a letter, and contain only letters, numbers and underscores. They are case-sensitive, and the prefixes firebase_, google_ and ga_ and certain names such as session_start are reserved.
How many parameters can a GA4 event have?
A standard GA4 property accepts up to 25 parameters per event. Parameter names can be up to 40 characters and values up to 100 characters.
Should I use GA4 recommended events or custom events?
Use a recommended event whenever one matches the action, such as generate_lead, sign_up or purchase. They feed built-in reports and other Google products. Use custom events only for actions Google doesn't cover.
Why are my GA4 custom event parameters not showing in reports?
Parameters are collected but only appear in standard reports after you register them as custom dimensions or metrics under Admin → Custom definitions. Data appears from that point on, not retroactively.
Are GA4 event names case-sensitive?
Yes. sign_up and Sign_Up are recorded as two separate events, which splits your data. Use lowercase snake_case for every event and parameter name.