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GPT-OSS 120b

OpenAI · USA
OpenAI's first major open-weights release. Apache 2.0, MoE with 5.1B active over 117B total, MXFP4 quantised to fit a single 80GB GPU. Historic shift for a vendor that built its brand on closed weights.
Licence facts
Licence
Apache 2.0
Commercial use
Unrestricted
Derivatives
Allowed
Attribution
Required
Parameters
117B MoE (5.1B active, MXFP4)
Runtime
Single 80GB GPU (H100 / MI300X)
Training data
Not disclosed
Prompt format
Must use OpenAI 'harmony' format
Last updated
2025-Q3
Known risks
  • Non-standard harmony prompt format locks integration work
  • Training data undisclosed
  • Reasoning model — chain-of-thought may leak sensitive logic
Sources
→ Model card→ Announcement→ Harmony format
See also
OpenAI API· API
Reviewed by Ali Madjaji · Last reviewed 2026-04-15
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