YouTube Data API

It exposes channels, videos, playlists, comments, captions and subscriptions, with authorised access needed for anything touching a specific account. Every project runs against a daily quota measured in units, search calls are capped separately and tightly, and running out stops the application until the quota resets, which is why analytics tools cache heavily and refresh on a schedule. This is also why third-party tools cannot show you everything Studio shows you. Impressions and click-through rate sit outside this API entirely, and several Studio figures are not exposed to anybody outside YouTube.