gpt-oss-20bOpen Weight
Released
gpt-oss-20b is an AI model released by OpenAI on Tuesday, Aug 5 2025, the same day as gpt-oss-120b. It is an open-weight model — the trained weights are available to download and run. It is a 21B parameter model with a 128k token context window. Benchmark results (shown below) cover SWE-Bench Verified, Humanity's Last Exam, GPQA Diamond, and MMLU.
Available from
| AkashML | — | $0.02 | $0.10 | 128K | fp4 |
|---|---|---|---|---|---|
| Darkbloom | — | $0.02 | $0.10 | 128K | fp8 |
| CoreWeave | — | $0.03 | $0.13 | 128K | fp4 |
| DeepInfra | — | $0.03 | $0.14 | 128K | bf16 |
| Parasail | — | $0.03 | $0.15 | 128K | fp4 |
| Novita | — | $0.04 | $0.15 | 128K | fp4 |
| Phala | — | $0.04 | $0.15 | 128K | — |
| Amazon Bedrock | — | $0.07 | $0.15 | 128K | — |
| Amazon Bedrock | eu-west-1 | $0.07 | $0.15 | 128K | — |
| SiliconFlow | — | $0.04 | $0.18 | 128K | fp8 |
| Together | — | $0.05 | $0.20 | 128K | — |
| Groq | — | $0.075 | $0.30 | 128K | — |
Benchmarks
Coding
Reasoning & science
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Frequently asked questions
gpt-oss-20b was released by OpenAI on Tuesday, Aug 5 2025.
gpt-oss-20b was built by OpenAI. Creators of ChatGPT and the GPT series of models. Pioneered large-scale language model research.
gpt-oss-20b reports 5 tracked benchmark scores — SWE-Bench Verified: 60.7%; Humanity's Last Exam (no tools): 10.9%; Humanity's Last Exam (with tools): 17.3%; GPQA Diamond: 71.5%; MMLU: 85.3%. Scores are the figures published at release by OpenAI.
gpt-oss-20b has a context window of 128k. That is the maximum amount of input plus output the model can hold in a single request.
gpt-oss-20b is reported at 21B parameters.
Partly. gpt-oss-20b is an open-weight model: the trained weights are free to download and run locally or on your own infrastructure, but the training data and code are not fully released and the license may restrict some commercial uses. It is not open source in the strict sense.
OpenAI's previous tracked release was gpt-oss-120b on Aug 5 2025. It was followed by GPT-5 on Aug 7 2025.