Stream = plays straight from YouTube (like YMusic), no wait, background + PiP. Download = keeps it offline in this browser.
Reads just the zip's file index (a few KB) over Drive, then downloads only the tracks you pick — the rest of a multi-GB archive is never fetched. Needs a browser with codecs your tracks use; compressed (non-Store) zip entries need DecompressionStream support (all current major browsers).
YouTube fetching needs the yt-dlp backend (media-backend/). Drive files and cached playback work without it. Files are cached in this browser (IndexedDB) and survive reloads. Lyrics and album art are read automatically from embedded MP3/M4A/FLAC tags.
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