How Deduplication of Conversions are Prevented
External ID is used for deduplication and it is used so that the reload of thank you page cannot create another conversion.
The External ID is a unique parameter of the conversion, and only one conversion with a given value can exist. An attempt to create another conversion with an already existing ID will end in an error, which will be recorded in the "Conversion error log".
So if a customer refreshes the page multiple times, will it trigger multiple sales?
The External ID parameter is used for this purpose in the conversion. This parameter is unique, so if an Order ID is entered into it, refreshing the page will not create another conversion. So this will prevent the redundant conversions.
What is the difference between External CID and External ID?
External CID is a help identifier that is used for pairing e.g. via email to create conversions. You can imagine it like the Click ID (CID), only pairing an external one (External CID).
External CID is in other words CID that comes from our client (our clients set these IDs)
External CID is added to a click by Set external CID script or via API
When saved to a click client can create conversions both via our CID or the External CID which was saved previously
External ID on the other hand is a parameter of conversion that is unique per system and is used for deduplication of conversions, for unique identification of them e.g. via adding charge ID.
It is used when changing status of conversion via API