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GPT-5.3 Codex vs Gemini 3 Flash
A detailed comparison of GPT-5.3 Codex (OpenAI) and Gemini 3 Flash (Google) across pricing, performance, and features.
Pricing Comparison
| Metric | GPT-5.3 Codex | Gemini 3 Flash | Difference |
|---|---|---|---|
| Input / 1M tokens | $2.00 | $0.50 | -75% |
| Output / 1M tokens | $16.00 | $3.00 | -81% |
| Context window | 200K | 1M | — |
| Max output | 65.536K | 65.536K | — |
Benchmark Comparison
| Benchmark | GPT-5.3 Codex | Gemini 3 Flash |
|---|---|---|
| MMLU-Pro | 90% | 78% |
| HumanEval | 96.5% | 90% |
| GPQA | 78% | — |
Capabilities
| Capability | GPT-5.3 Codex | Gemini 3 Flash |
|---|---|---|
| code | ✓ | ✓ |
| reasoning | ✓ | ✓ |
| text | ✓ | ✓ |
| tool-use | ✓ | ✓ |
| vision | ✓ | ✓ |
GPT-5.3 Codex Strengths
- ✓Best coding model from OpenAI
- ✓Large output window (65K tokens)
- ✓Strong reasoning for complex tasks
GPT-5.3 Codex Weaknesses
- ✗API access not yet available
- ✗Premium pricing
Gemini 3 Flash Strengths
- ✓1M context at budget pricing
- ✓Very fast
- ✓Free tier available via Google AI Studio
Gemini 3 Flash Weaknesses
- ✗Less capable than Pro on complex reasoning
- ✗Audio input priced separately ($1/1M)
Quick Verdict
Best value: Gemini 3 Flash is the more affordable option at $0.5/$3 per 1M tokens.
Higher benchmarks: GPT-5.3 Codex scores higher on average across available benchmarks (88.2% avg).
Larger context: Gemini 3 Flash supports 1M tokens.
Choose Gemini 3 Flash if cost matters most. Choose GPT-5.3 Codex if you need the best possible quality for complex tasks.