Overview
gpt-oss-120b is an open-weight language model from OpenAI, released under the Apache-2.0 license.
- License: Apache 2.0
- Context length: 128K tokens
- Languages: Multilingual
- Minimum hardware: ~80 GB VRAM
- Strengths: frontier open-weight reasoning and tool use
Highlights
- Permissive Apache 2.0 — no copyleft or patent risk, cleared for commercial deployment.
- Configurable reasoning effort — set low, medium, or high to trade quality against latency.
- Full chain-of-thought — complete access to the model's reasoning for debugging and trust.
- Agentic capabilities — native function calling, web browsing, Python execution, and structured outputs.
- MXFP4 quantization — MoE weights post-trained in MXFP4 so it runs on a single 80GB GPU (H100 / MI300X).
What it is good at
The capability tags on gpt-oss-120b are tools, thinking, reasoning, and code. Those map onto a few concrete jobs:
- Agentic tool use — native function calling lets the model trigger searches, run code, or hit local tools and fold the results back into its answer.
- Step-by-step reasoning — it exposes its chain of thought and supports adjustable reasoning depth, useful for math, planning, and multi-step problems. OpenAI reports it lands near o4-mini on core reasoning benchmarks.
- Coding help — writing, explaining, and debugging code, including longer files that benefit from the 128K context.
Running it locally
gpt-oss-120b reports a 120.4B parameter count, and OpenAI ships the checkpoint in MXFP4 form at roughly 61 GiB. The clean target for local serving is a single 80 GB GPU such as an H100; setups with less VRAM can run it through CPU offloading at lower speed. The 128K context window means you can feed it large documents or long chat histories.
huggingface-cli download openai/gpt-oss-120b
From there you can serve it with Transformers or vLLM, or load it in Atomic Chat with one click and start chatting fully on-device.
License
gpt-oss-120b is released under Apache-2.0. You can use it commercially, modify it, fine-tune it, and ship products built on it, with no copyleft requirement and an explicit patent grant. Keeping the license notice is the main obligation.