firstrun is one self-hosted analytics backend for everything you ship. Your marketing site, your desktop app, your mobile app and your backend all report into one project, on your own Postgres, and you read them on one board.
Every event is one you named. There is no fixed funnel and no privileged event: a download button is track("download_clicked") and is treated exactly like anything else you send. Ordinary web analytics (page views, sessions, referrers, Core Web Vitals) is measured for you underneath that, so nobody has to run a second tag alongside this one.
These guides are written with placeholder keys. Sign in and pick one of your sources in the header, and every snippet below is rewritten with its real source key and the origin it should report to, so there is nothing left to substitute by hand.