NeoBERT: A Next-Generation BERT

TL;DR

NeoBERT introduces a next-generation encoder that combines architectural innovations, modern data, and optimized pre-training to outperform existing models like BERT and RoBERTa on multiple benchmarks, with a compact size and seamless integration.

Contribution

It presents NeoBERT, a new encoder model that integrates state-of-the-art advancements, achieving superior performance with a compact design and extended context length.

Findings

Outperforms BERT large and RoBERTa large on MTEB benchmark.

Achieves state-of-the-art results with only 250M parameters.

Demonstrates effectiveness across GLUE and MTEB evaluations.

Abstract

Recent innovations in architecture, pre-training, and fine-tuning have led to the remarkable in-context learning and reasoning abilities of large auto-regressive language models such as LLaMA and DeepSeek. In contrast, encoders like BERT and RoBERTa have not seen the same level of progress despite being foundational for many downstream NLP applications. To bridge this gap, we introduce NeoBERT, a next-generation encoder that redefines the capabilities of bidirectional models by integrating state-of-the-art advancements in architecture, modern data, and optimized pre-training methodologies. NeoBERT is designed for seamless adoption: it serves as a plug-and-play replacement for existing base models, relies on an optimal depth-to-width ratio, and leverages an extended context length of 4,096 tokens. Despite its compact 250M parameter footprint, it achieves state-of-the-art results on the massive MTEB benchmark, outperforming BERT large, RoBERTa large, NomicBERT, and ModernBERT under identical fine-tuning conditions. In addition, we rigorously evaluate the impact of each modification on GLUE and design a uniform fine-tuning and evaluation framework for MTEB. We release all code, data, checkpoints, and training scripts to accelerate research and real-world adoption.