title: Closed-weight models
aliases: [closed-weight, closed-weight model, proprietary model, proprietary API]
tags: [term]
category: AI & NLP
summary: A model whose parameters are kept private, usable only by sending input to the owner's servers through an API.

Closed-weight models

A model is closed-weight when its trained parameters (weights) are kept private by the company that made it. You cannot download it or run it yourself and the only way to use it is to send your input over the internet to the company's servers and get a result back. Most of the best-known commercial systems (the models behind tools like ChatGPT, Gemini, and Claude) are closed-weight.

This is the opposite of an open-weight model, which you can download and run on your own hardware.