High-Fidelity Audio, No Subscriptions
Play your local music collection in the quality it deserves. No streaming, no ads, no subscriptions.
Hi-Res Playback
Play FLAC, ALAC, and MP3 files directly from the Files app with advanced in-place linking — no importing required.
Professional EQ
Dial in your sound with a 5-band or professional 10-band ISO Equalizer. Save custom EQ profiles per album or playlist.
Reactive Visualizers
Watch your music come alive with Aurora backgrounds, Ripple fields, and themed visuals including Sakura, Tokyo Tower, and more.
Discovers What You've Forgotten
The on-device recommendation engine learns your listening habits by time, day, and season — then surfaces personalized daily suggestions through the "Forgotten Gems" feature.
100% Offline & Private
Every feature runs entirely on-device. Your music library is never uploaded, analyzed by a server, or shared with anyone. OS-39 doesn't collect any data.
OS-39 Pro
Unlock the full listening experience with a single one-time purchase. No subscriptions.
Gapless Playback & Crossfade
Listen to albums as they were meant to be heard, with seamless track transitions and customizable crossfade.
Full 10-Band EQ & Themes
Access the professional 10-band ISO Equalizer and unlock all premium aesthetic themes and exclusive visualizers.
Enhanced Library Intelligence
Unlock deeper recommendations, extended Forgotten Gems history, and smarter seasonal suggestions.
Frequently Asked Questions
What audio formats does OS-39 support?
OS-39 supports FLAC, ALAC (Apple Lossless), and MP3. Files are played directly from the Files app with no importing step needed.
Do I need a subscription?
No. OS-39 is free with core playback features, and a single one-time Pro purchase unlocks gapless playback, the full 10-band EQ, all themes, exclusive visualizers, and enhanced recommendations.
Is my music library private?
Completely. OS-39 operates 100% offline with no data collection. Your library, listening habits, and preferences never leave your device.