You can find the engine used here [1], the API built around it here [2] and its WASM port here [3] and the WebAssembly matrix multiplication optimizations are here [4]

[1] https://marian-nmt.github.io/

[2] https://github.com/browsermt/bergamot-translator

[3] https://github.com/browsermt/bergamot-translator/tree/main/w...

[4] https://github.com/mozilla/gecko-dev/tree/master/third_party...