  We introduce CroissantLLM, a 1.3B language model pretrained on a set of 3T
English and French tokens, to bring to the research and industrial community a
high-performance, fully open-sourced bilingual model that runs swiftly on
consumer-grade local hardware. To that end, we pioneer the approach of training
an intrinsically bilingual model with a 1:1 English-to-French pretraining data
ratio, a custom tokenizer, and bilingual finetuning datasets. We release the
training dataset, notably containing a French split with manually curated,
high-quality, and varied data sources. To assess performance outside of
English, we craft a novel benchmark, FrenchBench, consisting of an array of
classification and generation tasks, covering various orthogonal aspects of
model performance in the French Language. Additionally, rooted in transparency
and to foster further Large Language Model research, we release codebases, and
dozens of checkpoints across various model sizes, training data distributions,
and training steps, as well as fine-tuned Chat models, and strong translation
models. We evaluate our model through the FMTI framework, and validate 81 % of
the transparency criteria, far beyond the scores of even most open initiatives.
This work enriches the NLP landscape, breaking away from previous
English-centric work in order to strengthen our understanding of
multilinguality in language models.
