An audio dashcam for your pocket. Save the riff you just played, the quote you almost missed, or the instructions you were just given. It keeps the last minutes of sound in RAM, sized to your phone, and writes to storage only when you tap Save.
Audio Blackbox is a free, open-source Android app that continuously keeps the last minutes of sound in RAM and writes them to local storage only when you explicitly tap Save. The rolling buffer is at least 5 minutes, set in 5-minute steps, and its maximum is computed on your phone from the memory it can safely use and the quality preset you pick.
It solves a problem a normal voice recorder cannot: you only realize something mattered after it was already said, once the recorder button is no longer any use. Audio Blackbox keeps recording into its own memory while its notification is showing, so tapping Save exports the buffered audio since your last save (the whole buffer the first time) as a local .m4a (AAC) file, no rewind needed, and files never overlap. It is made for musicians and songwriters, for ideas and thinking out loud, for meetings and agreements you are part of, and for family moments.
Unlike a normal recorder or a cloud-backed transcription app, Audio Blackbox has no INTERNET permission in its manifest, no analytics SDK, and no account: nothing is written to disk until you decide to save it, and the app never uploads anything.
You only know something mattered after it was said. These are the moments Audio Blackbox is built for.
Keep the riff or melody you just improvised, without having pressed record first.
A backup for the quote that came before you hit record on your main recorder.
Keep the explanation you just missed, in classes where recording is allowed.
Replay instructions, directions or details you were just told. Helpful for anyone who loses track of spoken information, for example people with ADHD. Not a medical device.
If something unexpected happens in traffic or on the street, save the minutes leading up to it.
The thought you said out loud, what was just agreed in a meeting you were part of, the first word at the dinner table.
Recording other people may require their consent, and the rules differ between countries and states. The notification stays visible the whole time the app is recording.
Continuous ambient capture without wearing out your SSD, draining your battery, or uploading a single byte to the cloud.
Just played a riff worth keeping, or said an idea out loud? Tap Save and Audio Blackbox writes the buffered audio since your last save (the whole buffer the first time) to a local file. Live keeps the buffered past and carries on recording until you stop.
INTERNET permission is strictly absent from the application manifest. It cannot send telemetry, ping analytics, or upload sound. Full offline guarantee.
Zero disk I/O and zero IPC allocations on the audio capture thread. Guaranteed single-writer synchronization eliminates dropouts and GC pauses.
When another foreground app takes the microphone, Android silences our stream rather than failing it. The service detects that directly and pauses, then resumes the moment the mic is free. The gap is preserved as true silence, so exported timestamps never drift.
Foreground service with active notification and guided manufacturer battery-optimization bypass keeps recording uninterrupted even with the screen off.
Listen, seek, delete, and share your saved .m4a (AAC) recordings through the Android share sheet. A home-screen widget starts or stops recording with one tap.
Test the interactive cockpit simulator: real-time VU meter, Korry annunciator status lights, "REMOVE BEFORE FLIGHT" safety tag, and flight tape memory buffer in your browser.
Audio Blackbox allocates its circular buffer up front, so its RAM cost is known before recording starts, and it only resizes a running buffer when the memory is there. Slide to see the RAM a window takes at each preset.
Built on Jetpack Compose and Material 3, dressed in a fixed cockpit palette — FED-STD-595 International Orange, NVIS green, Korry annunciator amber — so the state of the recorder reads at a glance.
Once installed, the app is a background service you rarely open: it listens, and you tap Save when something is worth keeping.
RECORD_AUDIO permission (and, on Android 13+, POST_NOTIFICATIONS) when prompted..m4a (AAC) file, and nothing needs to be pre-armed or predicted.Free, open source, and available now for Android 10 and newer.
Open the listing on your Android device and tap Install. No account sign-ups, no invitations.
Open Play Store →Yes. Audio Blackbox keeps the last minutes of sound in your phone's RAM while its notification is showing. The buffer is at least 5 minutes, set in 5-minute steps, and can be longer: the app computes the maximum on your phone from the memory it can safely use and the quality preset you pick. Tap Save and the buffered audio since your last save (the whole buffer the first time) becomes a local .m4a (AAC) file.
A normal recorder cannot do this, because it only starts capturing when you press record. With Audio Blackbox, you turn on continuous recording once and it keeps the most recent minutes in a rolling RAM buffer, replacing the oldest audio with the newest. When something worth keeping just happened, tap Save to write those minutes to a file. Nothing is written to storage until you tap Save.
It is a recorder that keeps capturing into a fixed-size memory buffer, so you can save what was already said instead of only what comes after you press record. Audio Blackbox works this way on Android: it runs as a foreground service with a persistent notification, holds the last minutes of audio in RAM, and discards the oldest audio as new audio arrives. Save exports the buffered audio, and Live keeps the buffered past and continues recording until you stop it.
At least 5 minutes, adjustable in 5-minute steps. There is no fixed maximum: the app computes the ceiling on your phone from the memory it can safely use and the quality preset you pick, and shows it in Settings. At the default Voice preset (16,000 Hz mono) each minute takes about 1.8 MB of RAM, so 30 minutes is about 55 MB. Balanced (32,000 Hz mono) uses twice that per minute and High fidelity (44,100 Hz stereo) about 5.5 times, so the same phone holds a shorter buffer at higher quality. The calculator in the Memory Architecture section of this page shows the RAM for any window and preset.
No. The INTERNET permission is strictly absent from the app's Android manifest, so it cannot send telemetry, ping analytics, or upload sound. The app never uploads anything: audio is kept in volatile RAM until you save it, then written to your phone's Recordings/Blackbox folder (Music/Blackbox on Android 10 and 11), where you control it.
Yes. Audio Blackbox runs as a foreground service with a persistent notification, and it includes a guided flow to bypass manufacturer battery optimization, so capture continues uninterrupted with the screen locked.
Audio Blackbox was measured on a Samsung Galaxy S25 recording continuously at the Voice preset: with the screen off it used about 1.0% to 1.5% of the battery per hour and under 1% CPU, with no disk writes while buffering. Other phones and settings will give different numbers.
Yes. It is free and licensed under the GNU General Public License v3.0, with the full source code published on GitHub.
Yes. Audio Blackbox is free on Google Play. The app has no account and no ads, and contains no analytics or trackers. It is licensed under the GNU General Public License v3.0 and its full source code is on GitHub, so anyone can check how the buffer and the save path work, and confirm that the manifest has no INTERNET permission.
Android 10 (API level 29) and newer.
Audio Blackbox is free on Google Play. Open its Play Store listing on your Android device and tap Install; the link is in the Download section of this page.
A normal recorder only captures audio after you press record, so anything said before that moment is lost. Audio Blackbox keeps recording continuously into a rolling RAM buffer and only writes to storage when you tap Save, so you can save the last minutes of something that already happened. Nothing is written to disk until you decide to save it, and the app never uploads anything.
Yes. Audio Blackbox works like a dashcam for sound: it keeps the last minutes in a rolling RAM buffer and writes them to a file only when you tap Save, so you can keep what happened just before. Unlike a hidden recorder, it always shows a notification while it is recording. Recording other people may require their consent, so check your local laws.
If Audio Blackbox was running, yes. Tap Save and the buffered minutes (at least 5, up to what your phone can hold) are written to an .m4a file, even though you never pressed record. Journalists can use it as a backup to their main recorder, and students can keep an explanation they just missed in classes where recording is allowed.
It can work as a memory aid. If you just heard directions, instructions or details and lost track of them, save the last minutes and replay them in the built-in player. This can help anyone who often loses track of spoken information, for example people with ADHD. Audio Blackbox is not a medical device.
It depends on where you are. Use Audio Blackbox for your own conversations and ideas. Recording other people may require their consent, and the rules differ between countries and states. Check your local recording laws before you record; you are responsible for how you use the app.