Fathom Analytics

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Build me privacy-first analytics I host myself, where a visitor cannot be followed across days.

STACK
- Node with Fastify, SQLite via better-sqlite3
- Server-rendered dashboard with inline SVG charts

COLLECTION
- One endpoint recording path, referrer, screen class and a site token, appended with a UTC timestamp
- No cookie, and no identifier that survives midnight

THE VISITOR KEY
- HMAC(ip + user-agent + site + UTC date, secret)
- Because the date is an input, the key changes every day and cannot be followed
- The raw IP and the raw user agent are discarded immediately, and the README says so

BOTS
- Filtered at ingest against a user-agent blocklist
- The dropped count is shown on the dashboard rather than hidden

SOURCES
- UTM parameters parsed into source, medium and campaign
- Referrers grouped by host, with the common aggregators normalised

DASHBOARD
- Date range, unique visitors, pageviews, top pages, top sources
- A daily chart that says plainly when a range has no data, instead of drawing a flat line
- A public mode behind an unguessable URL, so stats can be shared without an account

RETENTION
- A nightly job rolling rows older than the window into daily aggregates

Include a README on the salt, the retention window and what is deliberately impossible to answer.