No cookies, no fingerprinting, no cross-site tracking, and no visitor identifier of any kind. Pick per site: zero-footprint retains no session key and no campaign tags; audience measurement retains both. Either way the only thing on the device is the opt-out flag and one ephemeral sessionStorage id that dies with the tab.
Pay per event, not per month. $10 covers 1M events - that's years of tracking for most sites.
Lightweight 2KB script. All your traffic sources, pages, and events in one view. Not real-time: events land in the dashboard within about 20 minutes.