JemRec

A call recorder for unrooted Android — phone and messenger calls.

Both sides of the call. No root, no computer, no second app — the phone sets itself up.

Website · Manual · Releases · Privacy policy · Support

Three looks - Memo, Deck and Multitrack - each light, dark or as the phone, in Settings → Theme.

The people in these screenshots do not exist: a screenshot of a call recorder is a screenshot of someone's calls, so the debug build invents them. Everything else is real.

Why JemRec

• Both sides of every call. Phone calls, and WhatsApp, Telegram, Viber and Google Meet calls on Android 14 or newer.
• No root, no computer, no second app. The phone pairs with its own Wireless debugging and sets itself up, once, in a few minutes.
• Nothing leaves your phone. No account, no cloud, no analytics. The only network JemRec uses is the phone talking to itself.
• It tells you when something is wrong. A recording that came out silent, a recorder that is down, a call that went by unrecorded - each gets a notification, so you do not find out on the day you need the call.
• Your rules. Record every call or be asked first, keep only some people's calls, and let old or very short recordings clear themselves away.
• Free, open and verifiable. Apache-2.0, and F-Droid rebuilds every release from this source and checks it matches, byte for byte.

Get started

1. Install it from F-Droid, or download the APK from Releases.
2. Follow the setup. JemRec walks you through it and watches for each step: one question (whether to hide Android's debugging notification), Developer options, USB and Wireless debugging (no cable needed), and pairing - the phone pairs with itself. Type the six-digit code into JemRec's notification, not the app: leaving Settings closes the code window. Once; the pairing survives restarts. OPPO, OnePlus and realme phones on their own systems (ColorOS, OxygenOS, realme UI) need one more switch in Developer options, Disable system optimization (Disable permission monitoring on older ones); setup names it.
3. Let it keep running: on phones that stop apps in the background (Honor, Huawei, Xiaomi, Samsung and others), setup asks you to allow JemRec in the phone's own screen for it, and tells you what to tap there. If the phone stops JemRec anyway, or holds it back while it restarts the recorder, a notification says so. The same screen is in Settings → Survive a restart.

Prefer to watch? The whole setup, start to finish, in 2:22 on YouTube, filmed on an Honor Magic 8 Pro.

Then run Settings → Diagnostics → Self-test. It answers, in about a second, whether your phone hands over both sides of a call.

The full manual, with what to do when a step misbehaves: on the web or in this repository.

F-Droid is the easy way: install the F-Droid client, search for JemRec, and updates arrive like any other app's. F-Droid is an installer the phone already trusts once you have allowed it, so nothing below applies.

The APK from Releases asks whether to allow installing from your browser or file manager; that is the sideload prompt. The two are the same file: F-Droid builds each tag on their own machine, checks the result against the APK here byte for byte, and publishes this project's signed APK rather than one of their own - so whichever way you installed, the other can update it in place, with no uninstall and no pairing again. Verified on 0.8: what F-Droid serves is byte-identical to jemrec-0.8.apk on the releases page, down to the signature.

Play Protect may get in the way, and what it takes differs by phone. It warns about apps it has not seen before, which is every app that is not on Play, so this is not a judgement about JemRec. Three phones, three outcomes:

Phone	What happened
Honor Magic 8 Pro	Installed with no complaint.
Galaxy S20	Refused. Turning Play Protect off long enough to install, then back on, worked. It is in the Play Store under your profile picture → Play Protect → Settings.
LineageOS	Refused from the browser. Opening the same file from the Files app installed it. Each app that can install needs Install unknown apps granted to it separately, and not every one of them is allowed to.

To check what you downloaded rather than trust it: every release is signed with the same certificate, and the release workflow prints its digest on each run:

apksigner verify --print-certs jemrec-0.8.apk
SHA-256: 50aeab3630f0198ea3845db51413b1ad29582f78240fa2df6fe55ba8537afdf8

A reboot kills the recorder, and building it again takes a few seconds of Wi-Fi. With auto-start allowed (on an Honor: Settings → Battery → App launch → JemRec → Manage manually, with Auto-launch on), the recorder was back ten seconds after Wi-Fi came on, with the app never opened. Without it, the phone declined to start the app at boot and nothing came back by itself - opening JemRec once had it recording sixteen seconds later. That is the fallback, and it always works.

On MagicOS 11 a restart also leaves Wireless debugging switched on without starting it. Since 0.25.1 JemRec sees that and switches it off and on itself: recording again eleven seconds after its first try, which came as the phone was unlocked, with the app never opened.

Wi-Fi is needed to rebuild the recorder, never to use it. Once it is up, recording carries on with Wi-Fi off, on mobile data, anywhere. The measurements are in How JemRec works.

[!IMPORTANT] Recording calls is your responsibility. Consent law differs by country and sometimes by state: one party, all parties, or a spoken notice. JemRec records what you tell it to and warns nobody on your behalf.

What you can do

Prefer to watch? What it does, in 1:51 on YouTube, on the app's own screens.

Record every call, or be asked	Automatic mode records every call; ask-first records nothing until you tap Record. A Quick Settings tile turns recording on and off, and a long press on it opens JemRec. → more
Start at the answer	Exact call tracking cuts the ringing, skips calls nobody answered, and splits call waiting into one recording per call. → more
Keep only the calls you want	All your contacts, all but some, only some, or none - and other numbers on their own switch. → more
Messenger calls	WhatsApp, Telegram, Viber, and Google Meet calls and meetings, both sides, each switched on separately, with the caller's name from the app's notification. Android 14+. → more
See every call	The Calls tab is your call log, each call with its recording - or, if there is none, why. Search either list, or narrow it with a tap. → more
Name files your way	By date and time, with the caller, or the way Honor's Phone app plays them from its call history. → more
Play, keep, clean up	A call plays as its waveform, to see where people talk, and plays on with the screen off, under the phone's media controls; a keep mark, a 30-day Recently deleted, and auto-delete for old or very short ones. → more

Recordings are Opus files in the phone's standard Recordings/JemRec folder, where any file manager or music app can open them - or in a folder you choose.

How it works

Android's voice-call audio source carries both sides of a call, but only system-level identities may read it - and the one an ADB session runs as, the shell, is among them. Getting a shell normally takes a computer, root, or a helper app like Shizuku. JemRec makes the phone its own computer:

flowchart LR
    subgraph phone["Your phone - nothing leaves it"]
        direction LR
        app["JemRec app"]
        adb["Wireless debugging<br/>(adbd)"]
        rec["Recorder<br/>runs as the shell"]
        file[("Recording<br/>Opus file")]
        app -- "① pairs over 127.0.0.1" --> adb
        adb -- "② starts it" --> rec
        rec -- "③ records both sides" --> file
        app -- "④ collects it,<br/>authenticated" --> rec
    end

1. The app pairs with the phone's own Wireless debugging - the same pairing a laptop does, with both ends on the same handset.
2. For a few seconds, it uses that session to start a small recorder that runs as the shell, then closes it. The recorder outlives the session.
3. The recorder watches the calls and writes each one to a file itself, so a phone that freezes background apps cannot cut a recording short.
4. The app collects the finished file over a socket on which the recorder and the app each prove who they are.

Wi-Fi is needed only to start the recorder - after a reboot, say - never to record. The full design, and the measurements behind each decision →

Phones and Android versions

	Phone calls	Messenger calls
Android 12 and 13	✓	— Android does not allow it
Android 14 and newer	✓	✓ WhatsApp, Telegram, Viber, Google Meet

Google Meet was tested on the Honor: calls both ways and a meeting. Signal takes the same path as the other messengers and has not been tested yet. Developer options and Wireless debugging are on every Android phone, though the menu they live in differs by make; JemRec names the right path for yours. OPPO, OnePlus and realme phones on their own systems (ColorOS, OxygenOS, realme UI) need one more switch there, and setup names that too.

Both sides of the call have been recorded on five phones, across three very different Android builds:

Phone	Build
Honor Magic 8 Pro (BKQ-N49)	MagicOS 10 and 11, Android 16 and 17 — the phone it was developed on
Samsung Galaxy S20	One UI
Samsung Galaxy S23	One UI, Android 16 — over Wi-Fi Calling too, which it carries like a messenger call
Samsung Galaxy M34	One UI 8.5, Android 16 — over Wi-Fi Calling too, since 0.24, as its owner reported
OnePlus	LineageOS 23

Five is not a compatibility list. The one thing nobody can promise for a phone they have not held is its audio hardware: some hand over both sides of the call, some one, some silence. The Self-test answers it on yours in about a second: it opens a real capture over the same path a call takes and tells you what came out of it.

The answering machine has been tried on two phones: the Honor, on 2G calls (its carrier would not register it for VoLTE), and a Galaxy S23 over Wi-Fi Calling. Whether a phone carries a greeting to the caller is up to its audio hardware too - Android's own answer was wrong on the Honor - so the answering machine's settings hold its own checks and a test call.

Privacy and permissions

• No microphone permission. The app never records; the recorder does the capturing - calls, and your answering-machine greeting.
• Nothing leaves the phone, and nothing is collected about you. Copy a report in Diagnostics puts how the last call was recorded on the clipboard, with no number, name or sound in it, only when you tap it.
• Calls and contacts only if you allow them - to name callers, keep calls by who they were with, and notice a call that went unrecorded. Everything works without them.
• No caller on the lock screen. While a recording plays, the phone's media controls name the caller only once it is unlocked; locked, they say Call recording.
• Debugging stays on while JemRec is on, because the recorder needs it; while it is off, it can go too (Settings → When JemRec is off). A computer you have paired with the phone can connect to it over the same Wi-Fi, and one you have authorised before over a cable; an unpaired one cannot. Now and then, check Wireless debugging → Paired devices and remove anything you do not recognise. With Start without Wi-Fi on, debugging port 5555 is open as well, to every network the phone joins, and announced there by the phone's serial number: a computer that reaches it, or an app on the phone, can ask to debug the phone, and the phone asks you - allow only one you expect. → What stays switched on

In the order F-Droid's listing page shows them, because a permission a call recorder does not explain is one its user has to guess at:

Permission	Why
INTERNET	Not about the internet: Android requires it for any TCP socket, including one to 127.0.0.1.
ACCESS_NETWORK_STATE	To tell whether there is Wi-Fi to rebuild the recorder over, instead of trying and failing.
WRITE_SECURE_SETTINGS	Granted by the app to itself over its own ADB session. Nothing but a shell can grant it, so no user can be talked into it. It lets JemRec switch debugging back on when the phone turns it off, and off with JemRec when you ask it to.
POST_NOTIFICATIONS	The recording notice, the ask-first prompt, the pairing code box.
FOREGROUND_SERVICE, FOREGROUND_SERVICE_SPECIAL_USE	To stay alive while a call is being recorded and while the finished file is collected; while the recorder is restarted after a computer's cable comes out; and for the seconds it takes to warn that the phone stopped JemRec in the background. SPECIAL_USE is the honest type: the microphone type would need a microphone permission this app does not hold.
FOREGROUND_SERVICE_MEDIA_PLAYBACK	To play a recording on with the screen off, under the phone's media controls. It plays; it never records.
RECEIVE_BOOT_COMPLETED	A reboot kills the recorder; this is what arms the job that rebuilds it.
READ_MEDIA_AUDIO	To list recordings made before a reinstall. Refusing it only hides those.
READ_EXTERNAL_STORAGE	Android 12 only, which has no READ_MEDIA_AUDIO: the same, to list recordings made before a reinstall. It covers photos and videos too; JemRec reads only its own folder. Refusing it only hides those.
READ_CALL_LOG, READ_CONTACTS	Optional. The only way to know who a call was with: to label a recording, to name a file after the caller, to keep or leave out a call by who it was with, and, for the call log, to notice a call that went unrecorded.
MANAGE_ONGOING_CALLS	For exact call tracking. Not one an app can ask for: the daemon allows it, as the shell, while the switch is on. Android then tells JemRec when each call is answered and ends. Tracking never acts on a call; the answering machine's answering is the recorder's, as the shell.

What is left out, and why, is in How JemRec works.

FAQ

Yes, where the phone's audio hardware hands both sides over - which it did on every phone above. The Self-test tells you for yours in about a second. In a messenger call each side has a channel of its own, you on the left and the other person on the right; a phone call has them so where the phone keeps the two apart, as the Honor does, and on others - a Pixel, by one report - both channels carry the same mix. On speakerphone, a messenger call's other person is heard on your side too: your side is the plain microphone, without the call app's echo cancellation. A call that still comes out with one side - over Wi-Fi Calling, say - is worth an issue on GitHub: tap Copy a report in Diagnostics right after it and paste that in.

Yes, calls and meetings, both sides, on Android 14 or newer - once you switch Google Meet on under Messenger calls. Like the messengers, it is off until you do. Meet puts its calls through Android's own call service, and up to 0.21 JemRec took them for phone calls and recorded every one, meetings included. Now a call is a phone call only when Android says the phone itself is in one.

On the two phones it has been tried on, yes. No app can play sound into a call, so the recorder does it as the shell: on the Honor through an output Android calls in-call music, on a Galaxy S23 over Wi-Fi Calling through Android's call-screening route; not every phone has either. Before you switch the answering machine on, its Checks tell you in a second whether yours does, and a Test call settles it for that kind of call: 2G, VoLTE and Wi-Fi Calling differ. Your microphone is muted while the greeting plays and the message is left, so the caller hears your greeting and nothing of your room.

Only to start the recorder: that is the one step that needs Wireless debugging, which Android runs over Wi-Fi. Once started, the recorder carries on with Wi-Fi off, on mobile data, anywhere. A reboot stops it, and the next few seconds of Wi-Fi bring it back by themselves (see Get started, step 3). Unplugging the phone from a computer can stop it too (a charger does not); on Wi-Fi it is back within seconds, by itself. With the screen off, step 3 matters here as well: without it, an Honor's battery manager kept the recorder down for about four minutes in two tests of three, and 8.5 minutes in another. Until then nothing is recorded - the header says so, a notification says the phone held JemRec back the moment it lets JemRec run again, and one says the recorder is down if it stays down two minutes. And if When JemRec is off is set to Turn all debugging off, turning JemRec back on needs Wi-Fi too.

Settings → Start without Wi-Fi takes the Wi-Fi away from all of that until the phone restarts: it opens debugging port 5555, which the recorder can be started over with no network at all. After a restart, the first start needs Wi-Fi once, as before. The cost is the open port, on every network the phone joins whenever USB debugging is on - unless Turn all debugging off goes with JemRec; see Starting without Wi-Fi.

Play removed call recorders in 2022 by forbidding the Accessibility API for recording, and no policy change since has re-opened the door. That is a distribution decision, not a technical one - the app itself never needed Play, and F-Droid asks only that a build be free software and reproducible from its source, which this one is. It never will be on Play.

It depends on where you and the other person are: some places need one party's consent, some everyone's, some a spoken notice. That is your responsibility; JemRec records what you tell it to and warns nobody on your behalf.

In the phone's standard Recordings/JemRec folder (or the folder you chose), as Opus files any music app can play; Share can also convert one to .m4a for iPhones and Macs. They are yours rather than the app's, so they stay when JemRec is uninstalled - delete them first if you want them gone. Deleted ones wait in Recently deleted for 30 days. Installed again, JemRec shows them as they were, once you let it read them (it asks): each recording carries its own marks - a message, kept, who a messenger call was with - inside the file.

Your phone refuses JemRec the one setting setup grants it until a switch of the phone's own is set, and the card names it. On an OPPO, OnePlus or realme phone it is Disable system optimization, the last switch in Developer options' Apps section (Disable permission monitoring on older ones; where it says just Permission monitoring, turn that off instead); some show it only in English, so if it is not there, set the phone's language to English, turn it on and set the language back. On a Xiaomi it is USB debugging (Security settings). Then tap Try again. Setup does not finish without that setting: it is what lets JemRec turn Wireless debugging back on after a restart. Leave it that way afterwards: the recorder needs it too, to turn debugging off when JemRec is uninstalled. Reported from two OnePlus phones (issues #61 and #64); we have none to try it on.

Choose in Settings → When JemRec is off what goes off with JemRec, then turn JemRec off - with the record button or the Quick Settings tile - before you open the bank:

• Hide Developer options: Developer options and Wireless debugging go off. USB debugging stays on, so JemRec keeps its recorder and turns back on instantly, anywhere.
• Turn all debugging off: USB debugging goes off too, and the recorder with it. Turning JemRec back on then needs Wi-Fi and takes about 15 seconds, and the answering machine is off until then. Away from Wi-Fi, JemRec asks first - unless Start without Wi-Fi is on (Settings → Debugging): then it comes back anywhere, on mobile data or none, until the phone restarts.

Try the first; if your bank still refuses, the second. With Start without Wi-Fi on, the first leaves debugging port 5555 open while JemRec is off, which a bank may look for too; the second closes it. Turning JemRec back on puts back what it switched off. Measured on an Honor (Android 17): with Developer options and Wireless debugging off, the recorder ran on through Wi-Fi off and on, a locked screen and a call, recorded both sides. Our own banks open with debugging on, so we could not test one that refuses - if yours needed the second choice, or neither worked, say so in issue #37.

Uninstall JemRec first. If the recorder is running, it notices the uninstall within a few minutes, turns both debugging switches off and exits - on an OPPO, OnePlus or realme phone only while its Disable system optimization switch is set as setup asked, or they stay on for you to turn off. Either way, once JemRec is gone nothing turns them back on. To have it off only while JemRec is off, see the question above.

Support JemRec

JemRec is free: no ads, no account, and nothing collected about you. If it has been useful to you, you can support its development on Donatello.

For developers

Build with JDK 21 (exactly - the daemon's bytes depend on it) and an Android SDK with platforms 37 and 36 and build-tools 36.0.0:

./gradlew assembleDebug     # build
./gradlew test              # 911 tests, screenshots of the screens included

How JemRec works	The design, the measurements behind it, every feature in depth, and every permission.
Developing JemRec	Building, the tests (logic, screenshots, emulator checks), and how a release reaches F-Droid.
SETUP.md	The end-user manual: every step, and what to do when one misbehaves. Generated by tools/build_site.py along with the same page on the site - edit it there, or the two drift.
ADB-NOTES.md	Four undocumented behaviours of the ADB library, each measured, each of which cost a day.
fastlane/metadata	The F-Droid listing: description, changelogs, icon and screenshots, written by tools/render_icon.py and tools/shoot.py alongside the README's.

Everything else that would have gone in a document is in the code, beside the thing it explains, with the measurement it came from.

Licence

Apache-2.0. See LICENSE, and NOTICE.md for what is vendored and under what terms — chiefly an audio-only fork of scrcpy's server in shellserver/, whose every modification is listed in shellserver/PATCHES.md.