openai

OpenAI: gpt-oss-20b (free)

by openai

OpenRouter
Tools Reasoning Long Context

About

gpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license. It uses a Mixture-of-Experts (MoE) architecture with 3.6B active parameters per forward pass, optimized for lower-latency inference and deployability on consumer or single-GPU hardware. The model is trained in OpenAI’s Harmony response format and supports reasoning level configuration, fine-tuning, and agentic capabilities including function calling, tool use, and structured outputs.

Specifications

Context Length 131K
Max Output Tokens 131K
Modality text->text
Input text
Output text
Supported Parameters include_reasoning, max_tokens, reasoning, seed, stop, temperature, tool_choice, tools
Content Moderation Yes

Error Rate

Based on feedback reported by Free LLM Router users. Error rate reflects the percentage of requests that encountered issues such as rate limiting, unavailability, or errors. Learn more.

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Availability

Available 41 of 41 tracked days. Daily snapshots show whether this model was accessible as a free model on OpenRouter.

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OpenAI: gpt-oss-20b (free)30

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Frequently Asked Questions

Is OpenAI: gpt-oss-20b (free) free to use?

Yes, OpenAI: gpt-oss-20b (free) is completely free to use through OpenRouter. You can access it via the Free LLM Router API at no cost.

What is the context window for OpenAI: gpt-oss-20b (free)?

OpenAI: gpt-oss-20b (free) supports a context window of 131K tokens (131,072 tokens).

What is the maximum output length for OpenAI: gpt-oss-20b (free)?

OpenAI: gpt-oss-20b (free) can generate up to 131K tokens (131,072 tokens) per response.

Does OpenAI: gpt-oss-20b (free) support function calling (tools)?

Yes, OpenAI: gpt-oss-20b (free) supports function calling / tool use, enabling it to interact with external APIs and services.

Does OpenAI: gpt-oss-20b (free) support reasoning?

Yes, OpenAI: gpt-oss-20b (free) supports reasoning capabilities, allowing it to show its step-by-step thought process.