OPT-66B

OPT-66B is the 66-billion-parameter member of Meta AI's Open Pre-trained Transformer family, released in May 2022 as part of an effort to give researchers full access to a GPT-3-class model. The OPT suite spans 125M to 175B parameters and was trained on a mix of RoBERTa, the Pile, and PushShift.io Reddit data with efficient distributed training techniques.

The release was a milestone for reproducible LLM research: Meta published model weights, training code, and development logs so the wider community could study robustness, bias, and toxicity in large models. The weights ship under a custom non-commercial license, so commercial deployment is not permitted; check the current license terms before any production use.