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Nuclear vs Kopuz: catalog facts
Nuclear	Kopuz
Free Free and open source under the AGPL-3.0 licence.	Free Free and open source under the EUPL-1.2, supported by sponsors.
Windows, macOS, Linux	Windows, macOS, Linux, Android
Streams from multiple sources, extendable with plugins Playlist import from other services and JSON files	Local files and many music services in one library Synced and word-timed lyrics display
Desktop only, no mobile app macOS may block the app on first launch	Apple Music playback only works on desktop Streaming sources need accounts with those services
Downloadable app	Downloadable app
Open source	Open source
License: AGPL-3.0-only	License: EUPL-1.2
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked October 1, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.