Gemini 2.5 Flash vs GPT-5-Codex
Google Gemini 2.5 Flash | OpenAI GPT-5-Codex | |
|---|---|---|
| Overview | ||
| Company | OpenAI | |
| Release date | Apr 17 2025 | Sep 15 2025 |
| Access | Proprietary | Proprietary |
| Benchmarks | ||
Nonsense detection BullshitBench v2Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better. | 19% | 39%Best |
| Timeline | ||
| Release gap | Gemini 2.5 Flash shipped 151 days before GPT-5-Codex | |
Which is better: Gemini 2.5 Flash or GPT-5-Codex?
GPT-5-Codex leads Gemini 2.5 Flash on 1 of the 1 benchmark they both report (BullshitBench v2). Gemini 2.5 Flash shipped 151 days before GPT-5-Codex, so benchmark comparisons should account for the intervening progress.
Published specifications for these two models are limited — see each model page for the latest details.
On BullshitBench v2, GPT-5-Codex leads at 39% vs Gemini 2.5 Flash at 19%.
Frequently asked questions
Gemini 2.5 Flash was released by Google on Apr 17 2025.
GPT-5-Codex was released by OpenAI on Sep 15 2025.
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