OPUS-MT

Web · Linux · Self-hosted · API

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Freedom report

One barScore 5.3

Free tierNo free tier on record
Open codeNo open-source code on record
Runs widely2 of 6 device platforms
DocumentedPlans, terms and facts published

OPUS-MT is ranked #53 of 154 in translation software on Freedom251. It runs on API, Linux, Self-hosted, Web.

Compared on translation software

API access: Yes

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The record

Purpose: OPUS-MT provides open neural machine translation models and tools for translation services.
Model foundation: The models are based on Marian-NMT and trained on OPUS data using OPUS-MT-train.
Model license: The repository says its downloadable pre-trained translation models are licensed CC-BY 4.0.
Web interface and API: One included setup is a Tornado-based web application with a web UI and API for multiple language pairs.
Deployment: The web application can be installed manually or run with Docker, including a documented CUDA GPU Docker option.
Linux service: The project documents installing a WebSocket translation service on Ubuntu.
Translation output: The WebSocket example returns translated text along with alignment and source and target segments.
Language pair configuration: The web server uses a JSON configuration to specify translation language pairs and model decoder configurations or remote hosts.
Translation workflow integration: The project points to OPUS-CAT as an NMT plugin for Trados Studio that can run OPUS-MT models.
Quality limitation: The maintainers caution that many automatic evaluation scores use simple, short Tatoeba sentences and may be too optimistic for realistic data.
Training limitation: The maintainers say the model training scripts are heavily customized for the University of Helsinki and CSC computing environment.
Model limitations: The maintainers state that current models lack filtering, data augmentation, domain adaptation, and quality control beyond automatic evaluation on selected test sets.

Where it ranks on Freedom251

Best Translation Software in 2026#53 of 154

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Sources

github.com/Helsinki-NLP/OPUS-MT· checked 5 Oct 2026
github.com/Helsinki-NLP/OPUS-MT/tree/master/doc/We· checked 5 Oct 2026