OpenAI has put out its first open-weight AI models since 2019, ending years of delay and speculation. The company released gpt-oss-120b and gpt-oss-20b on Tuesday, offering two fully downloadable, customizable large language models that don’t require a license fee or API gate.
Both models are text-only and are being shared under an Apache 2.0 license, meaning anyone can download the model weights from platforms like GitHub and Hugging Face.
They also work on LM Studio and Ollama, and can run on everything from laptops to cloud servers. OpenAI said the models are optimized to function across a range of hardware, including consumer devices and chips from Nvidia, AMD, Cerebras, and Groq.
OpenAI trained models to block malicious fine-tuning
OpenAI said it delayed releasing the models to complete safety evaluations. During pre-training, the company filtered out sensitive material, specifically chemical, biological, radiological, and nuclear data. It also tested scenarios where bad actors might try to fine-tune the models for malicious tasks.
The company reported that none of those experiments led to models reaching its internal “high capability” threshold, a classification outlined in its Preparedness Framework, which it uses to assess harm potential.
Greg Brockman, OpenAI’s president, told reporters, “It’s been exciting to see an ecosystem develop, and we are excited to contribute to that and really push the frontier and then see what happens from there.”
He added that the company also included three external expert groups to audit and comment on the fine-tuning of safety tests. These models aren’t open-source in the traditional sense.
OpenAI is only providing the model weights, not the full training code or datasets. But they are still open enough to allow users to test, fine-tune, and deploy them however they see fit. The company framed this as a middle ground between full transparency and maintaining some control.
Amazon, Microsoft, and Anthropic expand AI marketplace
The models will also be available through cloud platforms. Amazon , Microsoft , and Baseten are offering gpt-oss-120b and gpt-oss-20b directly to customers.
This is the first time Amazon Web Services (AWS) will host OpenAI models, and they will be accessible through both Bedrock and Sagemaker. Amazon said these models will help customers build AI agents capable of advanced reasoning and step-by-step thinking.
Andy Jassy, CEO of Amazon, has positioned AWS as a marketplace where companies can pick from multiple AI providers, not just Amazon’s in-house tools. In addition to OpenAI, Amazon has also partnered with Anthropic, putting $8 billion into the AI startup.
That deal lets AWS clients access Anthropic’s Claude models. On Tuesday, Anthropic said it would release a new Claude model, which it claims is better at coding, research, and data analysis than its previous versions.
The release puts OpenAI in the same lane as other companies offering open-weight models, like Meta, Mistral AI (which is backed by Microsoft), and DeepSeek, a Chinese startup that previously gained attention for building an AI model with human-like reasoning.
Jensen Huang, CEO of Nvidia, said, “OpenAI showed the world what could be built on Nvidia AI — and now they’re advancing innovation in open-source software.” Nvidia partnered with OpenAI to make sure the models perform well across its hardware. So did AMD, Cerebras, and Groq, giving users more flexibility when choosing where to run the models.
Both gpt-oss-120b and gpt-oss-20b support chain-of-thought processing, tool usage, and tasks that require multi-step reasoning. Users can run them locally or in the cloud without needing to call an API or rely on a paid plan.
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