| What you can do | ClosedAPI only | Open weightsParameters published | Open-source AIOSI definition 1.0 |
|---|---|---|---|
| Use it through an app or API | Yes | Yes | Yes |
| Download and run it yourself | No | Yes | Yes |
| Change it on your own computers | No | Yes | Yes |
| Read the complete training code | No | Rarely | Yes |
| Detailed information about the training data | No | Rarely | Yes |
| Maker can patch or switch off every copy | Yes | No | No |
| Examples | Gemini 4 Argon · Claude Opus 4.6 · Claude Fable 5 | Kimi K3 · MiMo-V2.6-Pro · GLM-5.3 | Weights, code and data information |
The short answerSome AI models stay with the company that made them. Others can be downloaded, so anyone can run them and change them.
In simple words
- Closed: you use it through the company’s app or website.
- Open: you can download it and run it yourself.
- Open models help researchers and keep data private.
- But the safety locks on an open model can be removed.
Two ways to share a model
A closed model is like a service you rent: you can use it, but it stays with the company. The company can change it or switch it off.
An open model is like a finished program you can download, copy and change. You can run it on your own computer, without sending your data anywhere.
Why it matters
Open models let researchers study AI and let companies keep their data private. But once a model is downloaded, anyone can remove the safety rules built into it.
Many strong open models now come from China, so open models are also part of the trade and chip debate.
Check yourself
What can you do with an open model?
Who controls a closed model?
What is a risk of open models?
0 of 3 answered
The short answerAn open-weights model can be downloaded and run by anyone; a closed model is used only through its maker’s app or API. Truly open-source AI also shares how it was built.
In simple words
- Closed models, such as GPT and Claude, run only on their makers’ servers.
- Open-weights models, such as Alibaba’s Qwen family, can be downloaded and changed.
- Open weights are not the same as open source, which also shares data information and code.
- Open models help research and privacy, but their safeguards are easier to remove.
Closed: use it, don’t hold it
A closed model stays on its maker’s computers. You reach it through an app or an API, and the maker can change it, filter it or switch it off.
That gives the maker control over misuse, and it keeps the model’s weights, its learned numbers, secret.
Open weights: download and run
An open-weights model publishes those numbers. Anyone can run it on their own hardware, adapt it or study it, without sending data to the maker.
Many strong open models now come from China, such as Alibaba’s Qwen family. That makes open models part of the chip and trade debate too.
Open weights are not open source
The Open Source Initiative’s definition says open-source AI must also share enough information about the training data, and the code, for others to rebuild and change it. Most models called open share only their weights.
Safety and the law
Once weights are public, safeguards can be removed, so researchers test how hard that is. The EU spares free and open-source models some documentation duties, unless they pose systemic risk.
From 2027, California also bars sites that offer model downloads from knowingly offering models that skip its required hidden labels.
Check yourself
What does an open-weights model share?
Is every open-weights model open source?
Why can open weights be a safety concern?
0 of 3 answered
The short answerOpenness is a spectrum: API-only access, open weights under licences of varying freedom, and open-source AI that also releases data information and complete code. Releases cannot be recalled, and EU law treats open-source models differently below the systemic-risk line.
In simple words
- Licences range from permissive ones, such as Apache 2.0 or MIT, to custom licences with limits.
- The OSI definition requires data information, complete code and the parameters.
- Fine-tuning can strip safeguards from open weights, and a release cannot be recalled.
- EU open-source models skip documentation duties, but not the copyright and summary duties.
What exactly is released
An open-weights release publishes the parameter files and usually code to run them. Licences range from permissive ones, such as Apache 2.0 or MIT, to custom licences that limit some uses or users.
Training data and the full training code are rarely released, which limits how far outsiders can reproduce or audit a model.
The Open Source AI Definition
The Open Source Initiative’s definition, version 1.0 from October 2024, asks for the freedoms to use, study, modify and share. It requires the preferred form for making changes: detailed data information, complete code for training and running, and the parameters.
Safety research on open weights
Research has shown that fine-tuning can remove refusal behaviour from open models at low cost, so labs test tamper resistance before release. Because copies spread beyond the maker’s control, a release cannot be recalled.
Supporters answer that open models let outsiders find flaws, run models privately and check claims, such as reproducible training runs.
The legal treatment
Under AI Act Article 53(2), general-purpose models released under a free and open-source licence with public parameters skip the technical documentation duties, unless they have systemic risk. They still need a copyright policy and a public training-content summary.
From January 1, 2027, California’s AB 853 bars generative AI hosting platforms from knowingly offering models that do not add the required provenance data.
Check yourself
What does the OSI definition require besides the parameters?
Which EU duties do open-source general-purpose models skip?
Why can an open-weights release not be recalled?
0 of 3 answered
Sources
- The Open Source AI Definition (Open Source Initiative)
- AI Act, Article 53 (EU AI Act Service Desk)
- AB 853 (California Legislature)
This lesson was generated by AI systems under the editorial rules of Silicon AI News and checked against the sources it lists. The live parts come from our checked stories, trackers, model comparison and rules checker.