This paper presents the hitherto largest pretraining dataset for the Scandinavian languages: the Scandinavian WEb (SWEb), comprising over one trillion tokens. The paper details the collection and processing pipeline, and introduces a novel model-based text extractor that significantly reduces complexity in comparison with rule-based approaches. We also introduce a new cloze-style benchmark for evaluating language models in Swedish, and use this test to compare models trained on the SWEb data to models trained on FineWeb, with competitive results. All data, models and code are shared openly. Large language models have made significant strides in recent years due to their general capabilities in language-processing tasks. This progress has been largely driven by the development of extensive and high-quality pretraining datasets sourced from open web data (Wenzek et al., 2020; Brown et al., 2020; Abadji et al., 2022; Penedo et al., 2023; 2024). However, the majority of research aimed at improving pretraining data focuses on high-resource languages such as English. Our goal is to create a large-scale and high-performing open pretraining dataset specifically for the Scandinavian (north-germanic) languages: Swedish, Danish, Norwegian, and Icelandic. Existing large-scale datasets for these languages primarily include mC4 (Xue et al., 2021), OSCAR (Abadji et al., 2022), and HPLT Datasets 1.2 (de Gibert et al., 2024). The Scandinavian portion of mC4 comprises approximately 100B tokens, 10B tokens for OSCAR 23.01, and 35B tokens for HPLT, which are all relatively small numbers considering that state-of-the-art large language models today are trained on trillions of high-quality tokens.

We have faced all of these challenges in our work on developing the first native LLM for the There is a growing interest in building and applying Nordic (or, more accurately, North Germanic) languages. Large Language Models (LLMs) for languages The LLM, which we call GPT-SW3, other than English. This interest has is a continuation of our previous Swedish-only been fuelled partly by the unprecedented popularity model (Ekgren et al., 2022), and is a collection of ChatGPT

Pre-training Large Language Models (LLMs) require massive amounts of text data, and the performance of the LLMs typically correlates with the scale and quality of the datasets. This means that it may be challenging to build LLMs for smaller languages such as Nordic ones, where the availability of text corpora is limited. In order to facilitate the development of the LLMS in the Nordic languages, we curate a high-quality dataset consisting of 1.2TB of text, in all of the major North Germanic languages (Danish, Icelandic, Norwegian, and Swedish), as well as some high-quality English data. This paper details our considerations and processes for collecting, cleaning, and filtering the dataset.