Key Takeaways
GPT-5 Codex wins:
- Larger context window
- Faster response time
- Higher intelligence benchmark
- Better at coding
- Better at math
GPT-5.1 Chat wins:
- No clear advantages in compared metrics
Price Advantage
GPT-5 Codex
Benchmark Advantage
GPT-5 Codex
Context Window
GPT-5 Codex
Speed
GPT-5 Codex
Pricing Comparison
Price Comparison
| Metric | GPT-5 Codex | GPT-5.1 Chat | Winner |
|---|---|---|---|
| Input (per 1M tokens) | $1.25 | $1.25 | Tie |
| Output (per 1M tokens) | $10.00 | $10.00 | Tie |
| Cache Read (per 1M) | $0.13 | $0.13 | Tie |
Both models have similar overall pricing.
GPT-5 Codex Providers
OpenAI $1.25 (Cheapest)
GPT-5.1 Chat Providers
OpenAI $1.25 (Cheapest)
Azure $1.25 (Cheapest)
Benchmark Comparison
6
Benchmarks Compared
0
GPT-5 Codex Wins
0
GPT-5.1 Chat Wins
Benchmark Scores
| Benchmark | GPT-5 Codex | GPT-5.1 Chat | Winner |
|---|---|---|---|
Intelligence Index Overall intelligence score | 44.6 | - | - |
Coding Index Code generation & understanding | 38.9 | - | - |
Math Index Mathematical reasoning | 98.7 | - | - |
MMLU Pro Academic knowledge | 86.5 | - | - |
GPQA Graduate-level science | 83.7 | - | - |
LiveCodeBench Competitive programming | 84.0 | - | - |
GPT-5 Codex significantly outperforms in coding benchmarks.
Cost vs Quality
X-axis:
Y-axis:
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GPT-5 Codex
Other models
Context & Performance
Context Window
GPT-5 Codex
400,000
tokens
Max output: 128,000 tokens
GPT-5.1 Chat
128,000
tokens
Max output: 16,384 tokens
GPT-5 Codex has a 68% larger context window.
Speed Performance
| Metric | GPT-5 Codex | GPT-5.1 Chat | Winner |
|---|---|---|---|
| Tokens/second | 162.0 tok/s | N/A | |
| Time to First Token | 10.44s | N/A |
Capabilities
Feature Comparison
| Feature | GPT-5 Codex | GPT-5.1 Chat |
|---|---|---|
| Vision (Image Input) | ||
| Tool/Function Calls | ||
| Reasoning Mode | ||
| Audio Input | ||
| Audio Output | ||
| PDF Input | ||
| Prompt Caching | ||
| Web Search |
License & Release
| Property | GPT-5 Codex | GPT-5.1 Chat |
|---|---|---|
| License | Proprietary | Proprietary |
| Author | OpenAI | OpenAI |
| Released | Sep 2025 | Nov 2025 |
GPT-5 Codex Modalities
Input
textimage
Output
text
GPT-5.1 Chat Modalities
Input
fileimagetext
Output
text