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.
- Both sides of every call. Phone calls, and WhatsApp, Telegram and Viber 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.
- Install it from F-Droid, or download the APK from Releases.
- 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.
- Let it start by itself after a restart: Settings → Survive a restart, on phones that keep such a list.
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.
Trouble installing? Play Protect, sideloading, and checking the APK
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
Why "start by itself" matters after a restart
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.
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.
| 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. → 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 and Viber, 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 |
| Hear about problems | A notification after each call, and one when a recording is silent, the recorder is down, or a call went unrecorded. → more |
| Answering machine | Off until you switch it on. Answers a phone call you have not taken after 5 to 30 seconds - after two rings when Do Not Disturb would silence the caller - plays the greeting you recorded and keeps the message, by the same rules as recording. Take the call or hang up from its notification while they speak. It stands down for a day after you call an emergency number. A test call tells you whether it works on your phone. → more |
| Three looks | Memo, calm and simple; Deck, a pocket recorder with an LCD and a REC key; Multitrack, a sound editor with a colour for each caller. Each light, dark or as the phone, in Settings → Theme. → 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.
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
- The app pairs with the phone's own Wireless debugging - the same pairing a laptop does, with both ends on the same handset.
- 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.
- 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.
- 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 →
| Phone calls | Messenger calls | |
|---|---|---|
| Android 12 and 13 | ✓ | — Android does not allow it |
| Android 14 and newer | ✓ | ✓ WhatsApp, Telegram, Viber |
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.
Both sides of the call have been recorded on four 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 |
| OnePlus | LineageOS 23 |
Four 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.
- 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.
- 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 installed, because the recorder needs it. 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. → What stays switched on
Every permission, and why
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. |
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. 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. |
USE_FULL_SCREEN_INTENT |
Lets the ask-first prompt last a minute instead of five seconds. Not auto-granted, and nothing is gated on it. |
WAKE_LOCK |
So the keep-alive job can finish its few seconds of work, and so a phone with its screen off stays awake while it brings the recorder back after a USB cable, a minute and a half at most. WorkManager declares it too. |
What is left out, and why, is in How JemRec works.
Does it really record both sides?
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. 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.
Will callers hear my greeting?
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.
Why does it need Wi-Fi?
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, the phone's battery manager kept the recorder down for about four minutes in two tests of three. Until then nothing is recorded - the header says so, and after two minutes a notification does too.
Why isn't it on Google Play?
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.
Is recording calls legal?
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.
Where are my recordings, and what happens to them if I uninstall?
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.
How do I turn debugging off for good?
Uninstall JemRec first. If the recorder is running, it notices the uninstall within a few minutes, turns both debugging switches off and exits; either way, once JemRec is gone nothing turns them back on.
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.
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 # 684 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.
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.