Nixie is local-first. It has no Nixie account, backend, telemetry, analytics, crash uploader, advertising SDK, or media cache.
The app stores playback restoration, preferences, bounded loudness measurements, recent searches, window bounds, and the YouTube parser cache on this computer. Website cookies remain in a dedicated Electron session. Lyrics are fetched when requested and are not persisted.
Signing in copies the YouTube cookies out of a browser profile you pick. Google expires that session every few minutes and only the browser holds the current value, so Nixie reads the same profile again while it runs, at most once a minute, for as long as the account stays linked. It reads the YouTube cookies and nothing else, it names the profile in a file in its own directory so it knows which one to read, and it writes nothing back to the browser. Signing out ends it. Those cookies are sent to YouTube, which is what makes the session work, and to nowhere else.
A play is reported to YouTube Music's watch history over the same signed-in session, once when it starts and once with the position it reached, so what you listen to here shapes the recommendations the app then shows you. Nothing about the play is kept locally, and turning off watch history in Settings stops the report. Apart from the update check described below, it is the only thing Nixie sends anywhere that was not asked for by a page you opened.
Settings reads and writes a handful of settings that belong to the linked account rather than to this computer: whether liked music from YouTube appears in your playlists, whether queues and radios update dynamically, and whether watch and search history are paused. Those are the account's own settings, so a change made here applies to every app signed in to it, exactly as it would if it were made in YouTube Music. They are read on request and never stored locally. Every other setting on that page, including theme, audio quality, normalization, content region, and restricted mode, stays on this computer and is sent nowhere.
Nixie asks GitHub for the latest release when it starts, and again whenever you press the button in Settings. That request carries no cookie and identifies neither the account nor the computer: GitHub receives it the way it receives any download, sees the address it came from, and applies its own policy. Nothing is downloaded until you ask for it, and a development build never asks at all.
Diagnostics are exported only when requested. Logs redact cookies, authorization values, signed URLs, lyrics, and media data.
YouTube Music, LRCLIB, and NetEase Cloud Music receive the requests needed to provide their services and apply their own policies. A lyrics lookup asks them in order and stops as soon as one answers, so the later sources are reached only when the earlier ones came back empty. LRCLIB and NetEase are sent a title, an artist, and a length, with no cookie and nothing that identifies the account. YouTube Music is asked over the same signed-in session that streams the audio, so that request is tied to the linked account like every other request to it. Clearing all local data removes Nixie state, measurements, and the website session.
Nixie is an independent, unofficial client. It is not affiliated with, endorsed by, or sponsored by YouTube, Google, Spotify, LRCLIB, or NetEase Cloud Music. YouTube and YouTube Music are trademarks of Google LLC, named here only to state which service Nixie connects to.