Swiss research institutions have released Apertus, claimed to be one of the world's largest fully open-source large language models, designed with transparency and regulatory compliance as core principles.

The model was developed by Swiss universities EPFL, ETH Zurich and the Swiss National Supercomputing Centre (CSCS) and made available through telecommunications provider Swisscom, AI platform Hugging Face, and the Public AI network on 2 September 2025.

Apertus, which is Latin for “open,” was designed to “set a new baseline for trustworthy and globally relevant open models,” according to the developers.

Unlike proprietary models from OpenAI, Anthropic and Google, Apertus provides complete access to its architecture, model weights, training data and development processes.

Apertus was developed with explicit consideration of Swiss data protection laws, copyright regulations, and transparency obligations under the EU AI Act. The training corpus uses only publicly available data, with filtering to respect Web site opt-out requests and remove personal information.

"With this release, we aim to provide a blueprint for how a trustworthy, sovereign, and inclusive AI model can be developed," said Martin Jaggi, Professor of Machine Learning at EPFL and member of the Swiss AI Initiative steering committee.

"Apertus is built for the public good. It stands among the few fully open LLMs at this scale and is the first of its kind to embody multilingualism, transparency, and compliance as foundational design principles", says Imanol Schlag, technical lead of the LLM project and Research Scientist at ETH Zurich.

For those outside of Switzerland, the Public AI Inference Utility will make Apertus accessible as part of a global movement for public AI.

"Currently, Apertus is the leading public AI model: a model built by public institutions, for the public interest. It is our best proof yet that AI can be a form of public infrastructure like highways, water, or electricity," says Joshua Tan, Lead Maintainer of the Public AI Inference Utility.