Open-weight model
Also called open weights, open-weights model
A model whose trained weights anyone can download and run on their own computer or servers.
Most famous chatbots run on closed models: you can use them, but only through the company's app or service. An open-weight model is published so that anyone can download the trained model itself, run it, adapt it or build on it.
That matters in two ways. Anyone can run it, the smaller ones even on a laptop, so your data need not leave your machine. And the same model can turn up in many different apps, each with its own rules, filters and data handling. "Open weights" isn't quite "open source": the training data and recipe are usually not published.
For example
DeepSeek, Qwen, Kimi and Meta's Llama release open-weight models, and OpenAI released 2, called gpt-oss, in August 2025.
Put it to use
Where you'll meet open-weight model in ChatGPT, Gemini and Claude, how to use it there, and the mix-up most people make.
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