sms-translate/README-translation.md

SMS translation fork of Fossify Messages

A small fork of Fossify Messages that auto-translates received SMS / MMS on-the-fly, on-device, with no cloud and no API keys.

Why this might be interesting

If you live somewhere where you get important SMS in a language you don't read fluently (bank alerts, delivery notifications, OTPs, government messages…), this lets you keep using a clean FOSS messaging app and still understand them.

The translation itself is sub-second per message, runs entirely on-device (Mozilla Bergamot / Marian NMT models), and preserves numbers and URLs verbatim — so OTP codes, account numbers, tracking links, etc. don't get mangled.

• Auto-translate: each received bubble swaps to its translation as it scrolls into view; conversation-list snippets do the same.
• Per-language opt-in: you choose which source languages get auto- translated (e.g. Korean → English) and which are left alone (e.g. Swedish, German, anything else you already read).
• Tap to flip: a small icon next to each translated bubble toggles it back to the original.
• Manual translate: long-press a bubble → ⋮ → Translate to force a one-off translation even for languages not on your auto-translate list.
• Copy / Share / Select capture what you see on screen — if the bubble is showing English, your clipboard gets English.

Screenshots

Conversation list	Thread (translated)	Thread (original toggled back)
Snippets are translated as you scroll, opted-in source languages only.	Auto-translate fires on view; the small icon below each bubble is the toggle. Numbers (145cm, 40kg, 112) and URLs (vo.la/1Pa9m) survive verbatim.	Tap the icon to flip a bubble back to its original. Tap again to flip back.

Translation settings	Manual translate (CAB ⋮)
Pick which source languages auto-translate and your target. Off by default.	Long-press → ⋮ → Translate to force a one-off translation for non-allowlisted languages.

Status — please read

This is an experiment, not a maintained project.

• No commitment to keep it up to date with upstream Fossify or with Android.
• No commitment to fix bugs or ship security updates.
• No releases on F-Droid or Play. Built and signed locally by the author.
• I'd like to propose the core feature upstream to Fossify Messages eventually; if they accept it, this fork's reason to exist mostly goes away. If they don't, I'll probably keep using my own build, but you should not depend on it.

If you want a clean, maintained build of Fossify Messages, install the official one from F-Droid. This fork is for tinkerers and for people who specifically want the translation behavior described above.

Dependencies

1. dev.davidv.translator — the offline-translator app on F-Droid. This is the engine. Install it, open it, download the language pack(s) for the languages you want to translate (e.g. Korean, the source side, plus the target language pack if it asks). It runs Mozilla's Bergamot translation models on-device.

   Without this app installed, the translation feature silently does nothing — the messaging app still works as a plain SMS client.

2. ML Kit Language Identification — bundled inside this APK (com.google.mlkit:language-id, Apache-2.0). Used only for detecting what language an incoming SMS is in, so we can decide whether to translate it. About 4 MB of model data baked in. This is transitional: if davidv accepts a small AIDL addition upstream (offline-translator issue) we'll drop ML Kit and use his detection directly.

3. Android 8.0+ (same as upstream Fossify).

How to use

1. Install offline-translator from F-Droid. Open it and download the language packs for the source language(s) you want translated (e.g. Korean) and confirm your target language pack is installed (usually English).
2. Install this fork's APK (build it yourself — see below).
3. Open this app → top-right ⋮ → Settings → Translation:
   • Turn on Translate received messages.
   • Pick your Translate into target (defaults to your device language).
   • Check the Auto-translate from languages you want auto-translated.
4. Open any conversation. Bubbles in opted-in languages translate as you scroll. Tap the small translate icon below a bubble to flip between original and translation.

How it differs from upstream Fossify Messages

The fork-only changes (not for upstream):

• Different package ID (net.jeena.smstranslate) so it installs alongside any official Fossify Messages.
• No "make me default SMS app" prompt on first launch. You can still make it the default via Android Settings → Default apps → SMS app if you want — this just doesn't pester you about it.
• Sideload warning suppressed. Fossify's built-in "this APK looks corrupted, go get the official one" dialog is silenced because of course this APK isn't the official one — it's a fork.

The translation feature itself lives in a separate :translate Gradle module and is structured so it can be cherry-picked onto upstream cleanly as a possible PR.

Building from source

You need JDK 17 and the Android SDK.

export JAVA_HOME=/path/to/jdk17
export ANDROID_HOME=/path/to/android-sdk
git clone <this repo>
cd sms-translate
./gradlew :app:assembleFossDebug
# APK at app/build/outputs/apk/foss/debug/messages-*-foss-debug.apk
adb install -r app/build/outputs/apk/foss/debug/messages-*-foss-debug.apk

If you want a release build, set up a keystore.properties per upstream Fossify's instructions and ./gradlew :app:assembleFossRelease.

License

Same as upstream Fossify Messages: GPL-3.0. The AIDL stubs from offline-translator are also GPL-3.0. ML Kit is Apache-2.0.

Credits

• Fossify Messages — the excellent FOSS messaging app this is a fork of.
• David Ventura — author of offline-translator, which does all the actual translation.
• Mozilla Bergamot — the underlying NMT models.