Key Takeaways
GPT-5.3 Codex wins:
- Larger context window
- Higher intelligence benchmark
- Better at coding
- Supports vision
Grok Code Fast 1 wins:
- Cheaper input tokens
- Cheaper output tokens
- Faster response time
- Better at math
Price Advantage
Grok Code Fast 1
Benchmark Advantage
GPT-5.3 Codex
Context Window
GPT-5.3 Codex
Speed
Grok Code Fast 1
Pricing Comparison
Price Comparison
| Metric | GPT-5.3 Codex | Grok Code Fast 1 | Winner |
|---|---|---|---|
| Input (per 1M tokens) | $1.75 | $0.20 | Grok Code Fast 1 |
| Output (per 1M tokens) | $14.00 | $1.50 | Grok Code Fast 1 |
| Cache Read (per 1M) | $0.17 | $0.02 | Grok Code Fast 1 |
Using a 3:1 input/output ratio, Grok Code Fast 1 is 89% cheaper overall.
GPT-5.3 Codex Providers
No provider data available
Grok Code Fast 1 Providers
No provider data available
Benchmark Comparison
6
Benchmarks Compared
3
GPT-5.3 Codex Wins
0
Grok Code Fast 1 Wins
Benchmark Scores
| Benchmark | GPT-5.3 Codex | Grok Code Fast 1 | Winner |
|---|---|---|---|
Intelligence Index Overall intelligence score | 54.0 | 28.7 | |
Coding Index Code generation & understanding | 53.1 | 23.7 | |
Math Index Mathematical reasoning | - | 43.3 | - |
MMLU Pro Academic knowledge | - | 79.3 | - |
GPQA Graduate-level science | 91.5 | 72.7 | |
LiveCodeBench Competitive programming | - | 65.7 | - |
GPT-5.3 Codex significantly outperforms in coding benchmarks.
Cost vs Quality
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Y-axis:
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Other models
Context & Performance
Context Window
GPT-5.3 Codex
400,000
tokens
Grok Code Fast 1
256,000
tokens
GPT-5.3 Codex has a 36% larger context window.
Speed Performance
| Metric | GPT-5.3 Codex | Grok Code Fast 1 | Winner |
|---|---|---|---|
| Tokens/second | 68.4 tok/s | 171.7 tok/s | |
| Time to First Token | 87.36s | 3.27s |
Grok Code Fast 1 responds 151% faster on average.
Capabilities
Feature Comparison
| Feature | GPT-5.3 Codex | Grok Code Fast 1 |
|---|---|---|
| Vision (Image Input) | ||
| Tool/Function Calls | ||
| Reasoning Mode | ||
| Audio Input | ||
| Audio Output | ||
| PDF Input | ||
| Prompt Caching | ||
| Web Search |
License & Release
| Property | GPT-5.3 Codex | Grok Code Fast 1 |
|---|---|---|
| License | Proprietary | Proprietary |
| Author | OpenAI | Xai |
| Released | Feb 2026 | Aug 2025 |
GPT-5.3 Codex Modalities
Input
textimage
Output
text
Grok Code Fast 1 Modalities
Input
text
Output
text