gpt-oss-20b
OpenAI · Released 5 Aug 2025 · gpt-oss-20b
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Input price / 1M tokens
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Output price / 1M tokens
131K
Context window
#68 of 71
180
Output tokens / second
#15 of 61
60.7%
SWE-bench Verified
#10 of 12
71.5%
GPQA Diamond
#24 of 27
98.7%
AIME 2025
#2 of 7
10.9%
Humanity’s Last Exam (no tools)
#21 of 23
Summary
gpt-oss-20b is an open-weight model from OpenAI, released on 5 Aug 2025.
Its 131K-token context window ranks #68 of 71.
Measured output speed is 180 tokens per second, #15 of 61.
OpenAI's smaller open-weight reasoning model (21B total, 3.6B active parameters), for low latency and local or on-device use. OpenAI says it is similar to o3-mini.
Benchmarks · 5 reported
| Benchmark | Score | Bar | Rank | Source |
|---|---|---|---|---|
| SWE-bench Verifiedhigh reasoning effort | 60.7% | #10 of 12 | OpenAI gpt-oss model cardSelf-reported | |
| GPQA Diamondno tools, high reasoning effort | 71.5% | #24 of 27 | OpenAI gpt-oss model cardSelf-reported | |
| AIME 2025with tools, high reasoning effort | 98.7% | #2 of 7 | OpenAI gpt-oss model cardSelf-reported | |
| Humanity’s Last Exam (no tools)no tools, high reasoning effort | 10.9% | #21 of 23 | OpenAI gpt-oss model cardSelf-reported | |
| MMLUhigh reasoning effort | 85.3% | – | OpenAI gpt-oss model cardSelf-reported |
Self-reported means the lab ran the test itself. A rank appears only where several labs report the same version of a benchmark.
Similar models
Models with the most benchmarks in common with gpt-oss-20b, and the closest scores.
SWE-bench Verified
#10 of 12Real GitHub issues, fixed and tested
- gpt-oss-20b60.7
- gpt-oss-120b62.4
- Gemini 2.5 Pro59.6
- Gemini 2.5 Flash60.4
- Gemini 3 Flash78
- Gemini 3.1 Pro80.6
GPQA Diamond
#24 of 27Graduate-level science questions
- gpt-oss-20b71.5
- gpt-oss-120b80.1
- Gemini 2.5 Pro86.4
- Gemini 2.5 Flash82.8
- Gemini 3 Flash90.4
- Gemini 3.1 Pro94.3
AIME 2025
#2 of 7Competition mathematics
Humanity’s Last Exam (no tools)
#21 of 23Expert questions, no search or code
- gpt-oss-20b10.9
- gpt-oss-120b14.9
- Gemini 2.5 Pro21.6
- Gemini 2.5 Flash11
- Gemini 3 Flash33.7
- Gemini 3.1 Pro44.4
Compare gpt-oss-20b side by side
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Sources
- context, max output, knowledge cutoff, parameters, license: developers.openai.com/api/docs/models/gpt-oss-20b, checked 2 Oct 2026
- release date Aug 5 2025, Apache 2.0, architecture: openai.com/index/introducing-gpt-oss/, checked 2 Oct 2026
- benchmarks: arxiv.org/html/2508.10925v1, checked 2 Oct 2026
- output speed: artificialanalysis.ai/models/gpt-oss-20b, checked 2 Oct 2026
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