Models & Architectures
Open-Weight Model in plain English.
Also known as: open weights,open-weights AI
The one-sentence version
A model whose trained parameters are published for anyone to download and run, even if the training data and code are not.
An open-weight model is one whose trained parameters — the billions of numbers that make it work — are released publicly, so anyone can download, run, fine-tune, and deploy it. This is narrower than "open source": the weights are open but the training data, the full training code, and sometimes commercial use may be restricted by licence. Llama, Qwen, DeepSeek, Gemma, Mistral, and GPT-OSS are open-weight; ChatGPT, Claude, and Gemini are not. Open weights matter because they let companies run models on their own infrastructure for privacy or cost reasons, let researchers inspect and modify them, and put a price floor under the whole market — a closed model has to be meaningfully better than the best free one to justify its fee. Their risk is that safeguards can be removed by whoever runs them.