Mozilla's Firefox Translations models for the keyboard's on-device translator (issue #424): the translate bar in the Smartbar translates what you type into the text field, entirely on the phone.
49 languages, both directions each. Mozilla trains every model to or from English, so a language here is two models — xx→en and en→xx — and a pair of two other languages is translated through English. Only models Mozilla has released in both directions are included: for each direction the "Release Android" model where Mozilla ships one to Firefox for Android (a smaller one than the desktop build), otherwise "Release". Languages released one way only (Croatian, Serbian, Albanian, Azerbaijani, Bosnian, …) are left out, and Norwegian is here once: Mozilla's no model is byte for byte its nb (Bokmål) one.
Files Three per direction — the model (model.xxen.intgemm.alphas.bin), the lexical shortlist (lex.50.50.xxen.s2t.bin) and the SentencePiece vocabulary (vocab.xxen.spm, or a srcvocab/trgvocab pair) — gzip-compressed exactly as Mozilla serves them. The app checks every file against the size and SHA-256 in TranslationModels.kt before unpacking it. A language costs 30–75 MB to download and 43–106 MB on the device; the base models are ~31 MB unpacked per direction, the "tiny" ones ~17 MB.
Why a copy here Every download in the app is a release asset of this repository, pinned by hash. Mozilla's own paths name the training run, which a newer model replaces. Mirrored and listed by tools/bergamot/prepare_models.py from Mozilla's registry of 2026-09-25; a newer set will be a new release, never a change to this one.
Source and licence Mozilla Firefox Translations models, © Mozilla, Mozilla Public License 2.0 — unchanged. Training pipeline and model source: https://github.com/mozilla/translations. Run by the Bergamot engine (MPL-2.0) and Marian NMT (MIT), built from the same repository by tools/bergamot/build-android.sh.