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OpenAI: Gpt-oss-120b (free)Reasoning. Local. Free.

Try OpenAI: Gpt-oss-120b (free)API Documentation

Deploy Enterprise Reasoning Locally

Near-Parity Performance

O4-Mini Level Reasoning

Matches OpenAI o4-mini on core benchmarks while running on single 80GB GPU.

Apache 2.0 Licensed

Build Without Restrictions

Commercial-grade freedom. No copyleft, no patent risk, full customization support.

Mixture-of-Experts

128 Experts, 4 Active

Efficient routing activates specialized experts per token for optimized inference.

Examples

See what OpenAI: Gpt-oss-120b (free) can create

Copy any prompt below and try it yourself in the playground.

Code Generation

“Write a production-grade Python function that implements a binary search tree with insert, delete, and search operations. Include comprehensive error handling and type hints.”

Mathematical Reasoning

“Solve this step-by-step: A rectangular garden is 24 meters long and 18 meters wide. If you want to build a path of uniform width around the perimeter, and the path area equals the garden area, what is the path width?”

Technical Documentation

“Create API documentation for a REST endpoint that accepts user authentication tokens and returns paginated results. Include request/response schemas, error codes, and rate limiting details.”

Data Analysis

“Analyze quarterly sales data trends across three regions and identify which product categories show growth potential. Recommend optimization strategies based on patterns.”

For Developers

A few lines of code.
Reasoning model. Zero cost.

ModelsLab handles the infrastructure: fast inference, auto-scaling, and a developer-friendly API. No GPU management needed.

  • Serverless: scales to zero, scales to millions
  • Pay per token, no minimums
  • Python and JavaScript SDKs, plus REST API
API Documentation 
import requests


response = requests.post(
    "https://modelslab.com/api/v7/llm/chat/completions",
    json={
  "key": "YOUR_API_KEY",
  "prompt": "",
  "model_id": ""
}
)
print(response.json())

FAQ

Common questions about OpenAI: Gpt-oss-120b (free)

Read the docs

GPT-OSS-120B is released as open-weight under Apache 2.0 license, allowing free download and local deployment without API costs. You run it on your own hardware instead of cloud infrastructure.

Yes. The model requires an 80GB GPU like H100 for full deployment, or you can use the lighter gpt-oss-20b variant on 16GB consumer hardware. Both support local inference via Ollama, LM Studio, or HuggingFace.

GPT-OSS-120B achieves near-parity with o4-mini on core reasoning benchmarks including coding, competition math, and tool use. It delivers comparable results at zero API cost when self-hosted.

GPT-OSS-120B supports 131,072 token context window and 131,072 max output tokens, enabling long-document processing and extended reasoning chains.

Yes. Full-parameter fine-tuning is supported, allowing you to adapt the model for domain-specific or task-specific applications without retraining from scratch.

Three configurable levels—low, medium, and high—let you trade latency for performance. Set reasoning effort in your system message for each request.

Ready to create?

Start generating with OpenAI: Gpt-oss-120b (free) on ModelsLab.

Try OpenAI: Gpt-oss-120b (free)API Documentation