mmBERT is a modern multilingual encoder that significantly outperforms previous generation models like XLM-R on classification, embedding, and retrieval tasks. Built on the ModernBERT architecture with novel multilingual training innovations, mmBERT demonstrates that low-resource languages can be effectively learned during the decay phase of training. It is also significantly faster than any previous multilingual encoder. mmBERT represents the first significant advancement over XLM-R for massively multilingual encoder models. Key features include: 1. Massive Language Coverage - Trained on over 1800 languages with progressive inclusion strategy 2. Modern Architecture - Built on ModernBERT…