OpenAI: gpt-oss-120b (free)

openai/gpt-oss-120b:free

Released Aug 5, 2025131,072 context

$0/M input tokens$0/M output tokens

gpt-oss-120b is an open-weight, 117B-parameter Mixture-of-Experts (MoE) language model from OpenAI designed for high-reasoning, agentic, and general-purpose production use cases. It activates 5.1B parameters per forward pass and is optimized to run on a single H100 GPU with native MXFP4 quantization. The model supports configurable reasoning depth, full chain-of-thought access, and native tool use, including function calling, browsing, and structured output generation.

Providers for gpt-oss-120b (free)

OpenRouter routes requests to the best providers that are able to handle your prompt size and parameters, with fallbacks to maximize uptime.

Performance for gpt-oss-120b (free)

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Actual cost per million tokens across providers over the past hour

Apps using gpt-oss-120b (free)

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Total usage per day on OpenRouter

Prompt

241M

Reasoning

20.1M

Completion

19.4M

Prompt tokens measure input size. Reasoning tokens show internal thinking before a response. Completion tokens reflect total output length.

Uptime stats for gpt-oss-120b (free)

Uptime stats for gpt-oss-120b (free) across all providers

Sample code and API for gpt-oss-120b (free)

OpenRouter normalizes requests and responses across providers for you.

OpenRouter supports reasoning-enabled models that can show their step-by-step thinking process. Use the reasoning parameter in your request to enable reasoning, and access the reasoning_details array in the response to see the model's internal reasoning before the final answer. When continuing a conversation, preserve the complete reasoning_details when passing messages back to the model so it can continue reasoning from where it left off. Learn more about reasoning tokens.

In the examples below, the OpenRouter-specific headers are optional. Setting them allows your app to appear on the OpenRouter leaderboards.

Using third-party SDKs

For information about using third-party SDKs and frameworks with OpenRouter, please see our frameworks documentation.

See the Request docs for all possible fields, and Parameters for explanations of specific sampling parameters.

gpt-oss-120b (free) - API Pricing & Providers | OpenRouter