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Find the configuration page of the Customer ID validation module by typing ‘Customer ID’ into the search bar of the under the Modules 
menu.
Guest events
The interface has only one configuration option.
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Read more about guest transactions in our API docs here.
Automatic customer ID generation
If the Customer ID validation is turned on, the customer ID is automatically generated when you add a new customer manually under the Customer insights menu.
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The generated ID cannot be modified with manual registration, however you’ll still be able to register customers with any customer ID via opt_in events, through the Events API.