Key Takeaways
GPT-5.3 Codex wins:
- Larger context window
- Higher intelligence benchmark
- Better at coding
- Supports vision
Mercury 2 wins:
- Cheaper input tokens
- Cheaper output tokens
- Faster response time
Price Advantage
Mercury 2
Benchmark Advantage
GPT-5.3 Codex
Context Window
GPT-5.3 Codex
Speed
Mercury 2
Pricing Comparison
Price Comparison
| Metric | GPT-5.3 Codex | Mercury 2 | Winner |
|---|---|---|---|
| Input (per 1M tokens) | $1.75 | $0.25 | Mercury 2 |
| Output (per 1M tokens) | $14.00 | $0.75 | Mercury 2 |
| Cache Read (per 1M) | $0.17 | $0.03 | Mercury 2 |
Using a 3:1 input/output ratio, Mercury 2 is 92% cheaper overall.
GPT-5.3 Codex Providers
No provider data available
Mercury 2 Providers
No provider data available
Benchmark Comparison
3
Benchmarks Compared
3
GPT-5.3 Codex Wins
0
Mercury 2 Wins
Benchmark Scores
| Benchmark | GPT-5.3 Codex | Mercury 2 | Winner |
|---|---|---|---|
Intelligence Index Overall intelligence score | 54.0 | 32.8 | |
Coding Index Code generation & understanding | 53.1 | 30.6 | |
GPQA Graduate-level science | 91.5 | 77.0 |
GPT-5.3 Codex significantly outperforms in coding benchmarks.
Cost vs Quality
X-axis:
Y-axis:
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Other models
Context & Performance
Context Window
GPT-5.3 Codex
400,000
tokens
Mercury 2
128,000
tokens
GPT-5.3 Codex has a 68% larger context window.
Speed Performance
| Metric | GPT-5.3 Codex | Mercury 2 | Winner |
|---|---|---|---|
| Tokens/second | 68.3 tok/s | 794.9 tok/s | |
| Time to First Token | 81.66s | 3.59s |
Mercury 2 responds 1064% faster on average.
Capabilities
Feature Comparison
| Feature | GPT-5.3 Codex | Mercury 2 |
|---|---|---|
| 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 | Mercury 2 |
|---|---|---|
| License | Proprietary | Proprietary |
| Author | OpenAI | Inception |
| Released | Feb 2026 | Mar 2026 |
GPT-5.3 Codex Modalities
Input
textimage
Output
text
Mercury 2 Modalities
Input
text
Output
text