Facebook/Instagram ads:

Facebook/Instagram app install ads require installation of SDK (Software Development Kit) into your app system, but does not require submission of website URL.

Google UAC & Apple app store:

Google UAC & Apple app store don't require installation of SDK to run app install ads, thus simply need to provide a website URL . Hence, we strongly recommend you to run these if the SDK isn't installed.

Please follow the link for more information about SDK.
Please follow the link for more information about mobile app ad creation.

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