Custom Events
If none of the previous event types covers the specific interaction you want to measure, then you will likely need to create a Custom Event. A custom event can be any event that you want to measure and is the reason that GA4 is a flexible platform. Using Custom Events will likely require a level of planning to ensure you can get the most out of your tracking setup and that it meets your needs.The easiest way to create and send custom events is through Google Tag Manager, but if you want to pass on parameters, you may need a developer to help set those up on your website.
Each custom event can support upto 25 custom parameters, though to gain value from them, they will need to be registered under Custom definitions as either a Custom Dimension or a Custom Metric. There is also a limit on the amount of Custom Definitions per property, with a maximum of 25 User Scoped and 50 Event scoped Custom Dimensions, as well as a maximum of 50 Event Scoped Custom Metrics. Custom Events also won’t show on many of GA4’s standard reports, so to take full advantage of them, you’ll need to use the Exploration reports to create your own custom reports.
When naming custom events, you should stick to the snake case naming convention (lowercase with the use of underscores, e.g add_to_cart) to keep consistent. Similarly, you should avoid using the same name as the other event types, otherwise you may see some odd numbers in your GA4 reports.