Use one stable, lower-case underscore style for your team, name each GA4 event for the action it measures, and put changing details in parameters. Google sets collection rules—including case sensitivity, allowed characters, reserved names and length limits—but does not require teams to use snake_case. A shared event registry and review process keep product, analytics, marketing and engineering aligned.
What should a GA4 event name describe?
An event name should identify the action you intend to measure. Use parameters to record additional or changing information about that action. This keeps one action under a stable name instead of creating a separate event for every variation.
For example, a lead form submission could use generate_lead when that recommended event matches the action. Record context such as form type or placement in parameters, rather than naming separate events for each form. Google describes event names as the chosen names for what a team intends to measure, with parameters providing details about what happened in its custom events guidance.
Choose one team style, then apply Google’s naming rules
Google does not prescribe a universal naming grammar such as snake_case. A practical house style is lower-case words separated by underscores: it is readable and uses characters Google permits. Whatever style you choose, document it and apply it consistently. GA4 event names are case sensitive, so capitalization differences create distinct event names.
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- Start event names with a letter.
- Use letters, numbers and underscores; do not use spaces.
- Keep event and parameter names within the 40-character limit specified in Google’s developer references.
- Check names against Google’s reserved event names, prefixes, parameter names and user-property names. Google says the lists are not exhaustive and may be updated periodically.
See Google’s current event naming rules before approving names. The rules also describe a specific exception involving automatically collected event names in certain Analytics create-or-modify-event workflows; that should not be treated as permission to send arbitrary reserved names through every implementation.
Check recommended events before creating custom ones
Before adding a custom event, compare the action with Google’s recommended events. Use a recommended event when its meaning matches the business action and its recommended parameters capture the context you need. Consider whether it fits the relevant web or app implementation, too.
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A custom event is appropriate when the recommended choices do not adequately represent what you need to measure. In that case, define its meaning and parameters deliberately; a custom name adds a definition your team must maintain in its tracking plan and reporting.
Respect parameter limits for the implementation you use
Google’s developer references specify a maximum of 40 characters for event and parameter names. The Measurement Protocol reference specifies up to 25 parameters per event and parameter-value limits of 100 characters for standard Analytics properties and 500 for Analytics 360 properties. Those figures are documented for the Measurement Protocol; check the reference for your collection method rather than assuming every implementation behaves identically.
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Google does not require a particular registry format. As a team governance practice, keep an event dictionary alongside the implementation so everyone uses the same definitions. For each event, record:
- Canonical name: the exact event name, with the team’s chosen casing and separators.
- Meaning and trigger: what the event represents and the precise condition that sends it.
- Parameters: each parameter’s definition, expected values and role as context.
- Owner: who approves changes and answers questions about the definition.
- Implementation surface: where it is implemented, such as a website or mobile app.
- Review status: whether the definition has been checked against recommended events, naming rules and current implementation needs.
Link the registry to Google’s naming rules and assign someone to recheck those rules during reviews, since Google may update its reserved lists. Route proposed additions and changes through the same review so teams do not create duplicate names or drift into competing definitions.
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