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Spek vs Sonic Visualiser: catalog facts
Spek	Sonic Visualiser
Free Free and open source under GPLv3.	Free Free and open source. Hosting, hardware and any external services are separate.
Windows, macOS, Linux	Windows, macOS, Linux
Shows instantly whether a lossless-looking file was upconverted from a lossy source Uses FFmpeg for decoding, so it opens the formats FFmpeg opens	Supports layered audio visualizations Works with analysis plug-ins
Development is quiet: the last release, 0.8.5, is from January 2023 It only views spectrograms; it cannot edit or convert anything	Designed for analysis rather than multi-track music production.
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0	License not stated
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 20, 2026	Official website Full listing and sources Checked September 22, 2026

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