Apertus: a fully open foundation model for sovereign AI

Apertus is a foundation model built on a fully open model: its weights, training data, code, methods and alignment principles are documented and reproducible. It is developed by the Swiss AI Initiative, a collaboration between EPFL, ETH Zurich and the Swiss National Supercomputing Centre (CSCS), and is presented as an open foundation model for sovereign AI.

The project states its approach plainly — Apertus is to AI what open source is to software. Because the whole training pipeline is published, researchers and companies can audit how the model was built instead of treating it as a black box.

Two sizes and more than 1,000 languages

The released models are competitive with leading open models at an equivalent scale of 8 billion and 70 billion parameters, according to the project. Apertus was multilingual from the start and trained on more than 1,000 languages, a deliberate choice for institutions that need models working in their own languages rather than in English alone.

Responsible training at scale

The project lists several techniques intended to make training responsible: respecting opt-outs from data holders, removing personal information from the training corpus and reducing memorization of training text. Documentation for these measures is published together with the weights.

Where to download and run it

The official weights are distributed through the swiss-ai organization on Hugging Face. Inference is offered by Swiss and international providers; Swisscom, a strategic partner of the Swiss AI Initiative, runs Apertus on its Swiss AI Platform, and the project also lists Infomaniak with a pay-per-token API and Phoeniqs.

Teams that prefer to host the model themselves can follow the project's quickstart for downloading the weights, and a community showcase collects applications built on Apertus. The pitch is aimed at organisations that want their AI stack under their own control: open weights can be inspected and served on local hardware, and no vendor can withdraw them.