What is each piece of information needed during the onboarding process, and why?

Identifier

Why

Ad account

Pulling marketing insights data (e.g. impressions, clicks, cost) to present on the Branch Dashboard.

Facebook App ID

Sending installs, opens and other events to Facebook in order to see whether they were driven by a Facebook ad campaign.

Facebook App Secret (Optional)

Used to create an app access token for deferred deep linking. The secret is not stored anywhere.