OpenAI: gpt-oss-20b✓ Catalog verified
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.
Overview
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.
Access: available through the official OpenAI API. Context window: 131K.
Specifications
| API identifier | openai/gpt-oss-20b |
| Provider | OpenAI |
| Model type | Text LLM |
| Context window | 131K catalog |
| Input modalities | text |
| Output modalities | text |
| Released | Aug 5, 2025 |
| Tokenizer | GPT |
| Moderated | No |
| Architecture modality | text->text |
API defaults
{
"top_p": null,
"temperature": null,
"frequency_penalty": null
}Pricing
Live pricing components for openai/gpt-oss-20b as published in the catalog.
| Pricing component | Raw unit price | Normalized | Unit |
|---|---|---|---|
| Prompt tokens | $3e-8 | $0.03 / 1M | Per input token |
| Completion tokens | $1.1e-7 | $0.11 / 1M | Per output token |
| Request fee | N/A | N/A | Per request |
| Image fee | N/A | N/A | Per image unit |
| Web search fee | N/A | N/A | Per search request |
Cost calculator
Estimate monthly spend from your own token volumes.
Estimated Total Cost
$0.04Calculated from current list pricing in the ModelsAtlas catalog.Capabilities
| Capability | Status | What it means |
|---|---|---|
| Visual Understanding | Not advertised | Image and document analysis support |
| Audio Processing | Not advertised | Speech and voice aligned flows |
| Tool Calling | ✓ Supported | Supports tools / function calling |
| Self-Hosting | Not advertised | Deploy outside managed APIs |
Capability signals
Directional signals derived from model metadata and capability tags — not official benchmark submissions.
Quick start
Call OpenAI: gpt-oss-20b through an OpenAI-compatible client.
from openai import OpenAI
client = OpenAI(
base_url="https://openrouter.ai/api/v1",
api_key="YOUR_API_KEY"
)
response = client.chat.completions.create(
model="openai/gpt-oss-20b",
messages=[{"role": "user", "content": "Explain quantum physics."}]
)
print(response.choices[0].message.content)Alternatives
Closest models by context window from a different provider.
| Model | Provider | Context | Input /1M | Actions |
|---|---|---|---|---|
| AionLabs: Aion-1.0 | Aion Labs | 131K | $4.00 | View → |
| AionLabs: Aion-1.0-Mini | Aion Labs | 131K | $0.70 | View → |
Sources & attribution
Pricing and metadata are maintained in the ModelsAtlas catalog.
Frequently asked questions
How much does OpenAI: gpt-oss-20b cost?
$0.03 per 1M input tokens and $0.11 per 1M output tokens on the official OpenAI API.
What is the context window of OpenAI: gpt-oss-20b?
OpenAI: gpt-oss-20b supports up to 131K tokens of context.
Does OpenAI: gpt-oss-20b support tool / function calling?
Yes, OpenAI: gpt-oss-20b supports tool / function calling — you can register tools and the model will emit structured tool calls.
How do I access OpenAI: gpt-oss-20b?
Use the official OpenAI API with the model id `openai/gpt-oss-20b`. See the Quick start section above for code examples.