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In plain English
An event says what happened; parameters give the details. A file_download event might carry file_name and file_extension, for example.
Each event can have up to 25 parameters. GA4 adds some automatically, such as page_location.
Parameters you send yourself won't appear in standard reports until you register them as custom dimensions or metrics. They do show in DebugView straight away, which can be confusing.
Example
Your generate_lead event sends form_name: 'quote_request'. To see form names in reports, register form_name as an event-scoped custom dimension. Reports show it from that point onwards.
Official documentation
- Set up event parameters (opens in a new tab) Google for Developers
- About events (opens in a new tab) Analytics Help
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