OpenAI gpt-oss-120b vs xAI Grok 4 Fast — side-by-side specs.
OpenAI gpt-oss-120b | xAI Grok 4 Fast | |
|---|---|---|
| Overview | ||
| Company | OpenAI | xAI |
| Release date | Aug 5 2025 | Sep 2025 |
| Model type | — | — |
| Open source | Yes | No |
| Specifications | ||
Parameters | — | — |
Context window | — | — |
| Benchmarks | ||
| Timeline | ||
| Release gap | gpt-oss-120b shipped 27 days before Grok 4 Fast | |
gpt-oss-120b and Grok 4 Fast don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. gpt-oss-120b shipped 27 days before Grok 4 Fast, so benchmark comparisons should account for the intervening progress.
gpt-oss-120b is an open-source / open-weight model; Grok 4 Fast is proprietary.
Direct benchmark comparisons are unavailable — gpt-oss-120b and Grok 4 Fast don't publish scores on any of the same benchmarks.