---
title: "Open-weight model"
description: "A model whose trained weights are published for download under a licence that may be permissive, copyleft, use-restricted or custom."
canonical: https://aigovernanceengineer.com/glossary/open-weight-model
author: "Jorge García Aibar"
license: "CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)"
doi: https://doi.org/10.5281/zenodo.22956197
version: "0.5.0"
updated: 2026-09-24
---

# Open-weight model

A model whose trained weights are published for download under a licence that may be permissive, copyleft, use-restricted or custom [1]. Open weights are not open source; the deployer produces almost all the evidence (hashes, scans, evals, red team) and must honour the licence and any acceptable-use policy.

- Developed in: [ch. 15, Open-weight licences](https://aigovernanceengineer.com/bok/governing-deployment#open-weight-licences); [ch. 18, Open-source carve-outs and their limits](https://aigovernanceengineer.com/bok/eu-ai-act#open-source-carve-outs-and-their-limits)
- Chapters: [ch. 15, Deployment](https://aigovernanceengineer.com/bok/governing-deployment) · [ch. 18, EU AI Act](https://aigovernanceengineer.com/bok/eu-ai-act)
- Contrast with: [Responsible-AI licence (OpenRAIL)](https://aigovernanceengineer.com/glossary/responsible-ai-licence-openrail)
- In the glossary chapter: https://aigovernanceengineer.com/bok/glossary#t-open-weight-model

## Sources

[1] Llama 3.1 Community License Agreement (an example of an open-weight licence with an incorporated acceptable-use policy and attribution terms). Meta. 2024-07-23. https://github.com/meta-llama/llama-models/blob/main/models/llama3_1/LICENSE (verified: primary)