The short version
Nothing you do on this site leaves your browser. There is no account, no analytics script, no advertising network, no tracking pixel and no third-party embed of any kind.
What is stored, and where
Three small preferences live in your browser’s own local storage: the colour theme you picked, whether you asked for left-handed diagrams, and the last root note you were working in so a bare chord index can resume where you left off. All three are readable only by this site, on this device, and clearing your browser data removes them.
What the server sees
The ordinary things any web server sees while answering a request: the page asked for, the time, and the network address it came from. Those are used to serve the page and to keep the site up, and nothing is joined across visits to build a profile.
Content security reports
If your browser blocks something on this site because it violates the page’s content security policy, it may post a short machine report describing what was blocked. Those reports carry no identity and exist so a broken page can be found and fixed.
Questions
If something on this page is unclear, or if you believe the site is doing something this page does not describe, say so — a privacy policy that is not true is worse than none.