Swiss AI Initiative

weights

open(Apache-2.0, BF16 safetensors)

data

open(full pretraining-data reconstruction scripts, github.com/swiss-ai/pretrain-data)

code

open(Megatron-LM training recipe + reconstruction scripts)

checkpoints

open(intermediate checkpoints on HF branches)

license

Apache-2.0(OSI)

The Apertus family's current release is the multimodal Apertus 1.5, shipped 2026-07-24. The 1.0/2509 release remains public with its full open stack: pretraining-data reconstruction scripts (respecting opt-out and robots.txt and stripping personal data), the Megatron-LM training recipe, intermediate checkpoints, and the technical report (arXiv 2509.14233), all Apache-2.0, which is the OLMo and Pythia full-openness tier. Apertus 1.5 is likewise Apache-2.0 and declares a 'fully open model: open weights + open data + open values + full training details including all data and training recipes', but its own multimodal-mix reconstruction scripts, training pipelines and intermediate checkpoints are announced as coming in the weeks ahead and have not shipped. The 5 therefore rests on the family's established practice and the still-public 1.0 stack rather than on the 1.5 promises. An Acceptable Use Policy accompanies the Apache-2.0 grant, restricting conduct (illegal or abusive use) rather than commerce or scale, so the license stays OSI.

• https://api.github.com/repos/swiss-ai/pretrain-data recorded 2026-08-14

  `private: false`, `archived: false`, license `Apache-2.0`, description "Pretraining data reconstruction scripts for Apertus". The reconstruction scripts are published, which is what satisfies data:open by reconstruction rather than by a released corpus.

• https://huggingface.co/swiss-ai/Apertus-70B-2509 recorded 2026-08-14

  Model card: "Fully open model: open weights + open data + full training details including all data and training recipes"; "Training Framework: Megatron-LM" linking github.com/swiss-ai/Megatron-LM; "The training intermediate checkpoints are available on the different branches of this same repository"; license apache-2.0; BF16 safetensors.

• https://ethz.ch/en/news-and-events/eth-news/news/2025/09/press-release-apertus-a-fully-open-transparent-multilingual-language-model.html recorded 2026-08-14

  ETH Zurich press release, title "Apertus: a fully open, transparent, multilingual language model", dated 2 September 2025 (EPFL/ETH/CSCS). Corroborates the release framing; establishes no dimension on its own, since a press release describes rather than exhibits the artifacts.

• https://github.com/swiss-ai/pretrain-data recorded 2026-08-14

  Repository page for the pretraining-data reconstruction scripts; "reconstruction" appears throughout the tree and README.

• https://huggingface.co/swiss-ai/Apertus-v1.5-70B recorded 2026-08-14

  Apertus-v1.5-70B model card: "Fully Open Model: Open weights + open data + open values + full training details including all data and training recipes"; License: apache-2.0; identifies itself as "Apertus 1.5 Omni, a multimodal assistant ... you understand images and audio and respond in text"; "context length up to 262,144 tokens, a four-fold increase from our initial Apertus 1.0 release"; and notes that "benchmark results, training pipelines, and intermediate checkpoints will be published in the coming weeks". Establishes weights and license for the current release; data/code for the v1.5 multimodal mix are declared but not yet shipped.