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Spek vs Spek-X: catalog facts
Spek	Spek-X
Free Free and open source under GPLv3.	Free Free and open source under the GPL.
Windows, macOS, Linux	Windows, 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	Spectrogram view of audio files Broad format support through FFmpeg
Development is quiet: the last release, 0.8.5, is from January 2023 It only views spectrograms; it cannot edit or convert anything	Fork with a small maintainer base Updates are infrequent
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0	License: GPL-3.0
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked September 20, 2026	Official website Full listing and sources Checked October 2, 2026

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