Key Takeaways
GPT-5.1-Codex-Mini wins:
- Higher intelligence benchmark
- Better at coding
- Better at math
Grok 4 Fast wins:
- Cheaper input tokens
- Cheaper output tokens
- Larger context window
- Faster response time
Price Advantage
Grok 4 Fast
Benchmark Advantage
GPT-5.1-Codex-Mini
Context Window
Grok 4 Fast
Speed
Grok 4 Fast
Pricing Comparison
Price Comparison
| Metric | GPT-5.1-Codex-Mini | Grok 4 Fast | Winner |
|---|---|---|---|
| Input (per 1M tokens) | $0.25 | $0.20 | Grok 4 Fast |
| Output (per 1M tokens) | $2.00 | $0.50 | Grok 4 Fast |
| Cache Read (per 1M) | $25000.00 | $50000.00 | GPT-5.1-Codex-Mini |
Using a 3:1 input/output ratio, Grok 4 Fast is 60% cheaper overall.
GPT-5.1-Codex-Mini Providers
OpenAI $0.25 (Cheapest)
Azure $0.25 (Cheapest)
Grok 4 Fast Providers
xAI $0.20 (Cheapest)
Benchmark Comparison
6
Benchmarks Compared
6
GPT-5.1-Codex-Mini Wins
0
Grok 4 Fast Wins
Benchmark Scores
| Benchmark | GPT-5.1-Codex-Mini | Grok 4 Fast | Winner |
|---|---|---|---|
Intelligence Index Overall intelligence score | 38.5 | 22.6 | |
Coding Index Code generation & understanding | 36.4 | 19.0 | |
Math Index Mathematical reasoning | 91.7 | 41.3 | |
MMLU Pro Academic knowledge | 82.0 | 73.0 | |
GPQA Graduate-level science | 81.3 | 60.6 | |
LiveCodeBench Competitive programming | 83.6 | 40.1 |
GPT-5.1-Codex-Mini significantly outperforms in coding benchmarks.
Cost vs Quality
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GPT-5.1-Codex-Mini
Other models
Context & Performance
Context Window
GPT-5.1-Codex-Mini
400,000
tokens
Max output: 100,000 tokens
Grok 4 Fast
2,000,000
tokens
Max output: 30,000 tokens
Grok 4 Fast has a 80% larger context window.
Speed Performance
| Metric | GPT-5.1-Codex-Mini | Grok 4 Fast | Winner |
|---|---|---|---|
| Tokens/second | 161.6 tok/s | 172.3 tok/s | |
| Time to First Token | 9.11s | 0.60s |
Capabilities
Feature Comparison
| Feature | GPT-5.1-Codex-Mini | Grok 4 Fast |
|---|---|---|
| Vision (Image Input) | ||
| Tool/Function Calls | ||
| Reasoning Mode | ||
| Audio Input | ||
| Audio Output | ||
| PDF Input | ||
| Prompt Caching | ||
| Web Search |
License & Release
| Property | GPT-5.1-Codex-Mini | Grok 4 Fast |
|---|---|---|
| License | Proprietary | Proprietary |
| Author | OpenAI | Xai |
| Released | Nov 2025 | Sep 2025 |
GPT-5.1-Codex-Mini Modalities
Input
imagetext
Output
text
Grok 4 Fast Modalities
Input
textimage
Output
text