Key Takeaways
GPT-5 Codex wins:
- Larger context window
- Faster response time
- Higher intelligence benchmark
- Better at coding
- Better at math
- Supports vision
- Supports tool calls
GPT-OSS-20b wins:
- Cheaper input tokens
- Cheaper output tokens
Price Advantage
GPT-OSS-20b
Benchmark Advantage
GPT-5 Codex
Context Window
GPT-5 Codex
Speed
GPT-5 Codex
Pricing Comparison
Price Comparison
| Metric | GPT-5 Codex | GPT-OSS-20b | Winner |
|---|---|---|---|
| Input (per 1M tokens) | $1.25 | $0.03 | GPT-OSS-20b |
| Output (per 1M tokens) | $10.00 | $0.14 | GPT-OSS-20b |
| Cache Read (per 1M) | $125000.00 | N/A | GPT-5 Codex |
Using a 3:1 input/output ratio, GPT-OSS-20b is 98% cheaper overall.
GPT-5 Codex Providers
OpenAI $1.25 (Cheapest)
GPT-OSS-20b Providers
DeepInfra $0.03 (Cheapest)
Parasail $0.04
Chutes $0.04
Novita $0.04
Clarifai $0.04
Benchmark Comparison
6
Benchmarks Compared
6
GPT-5 Codex Wins
0
GPT-OSS-20b Wins
Benchmark Scores
| Benchmark | GPT-5 Codex | GPT-OSS-20b | Winner |
|---|---|---|---|
Intelligence Index Overall intelligence score | 44.5 | 24.5 | |
Coding Index Code generation & understanding | 38.9 | 18.5 | |
Math Index Mathematical reasoning | 98.7 | 89.3 | |
MMLU Pro Academic knowledge | 86.5 | 74.8 | |
GPQA Graduate-level science | 83.7 | 68.8 | |
LiveCodeBench Competitive programming | 84.0 | 77.7 |
GPT-5 Codex significantly outperforms in coding benchmarks.
Cost vs Quality
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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-OSS-20b
131,072
tokens
GPT-5 Codex has a 67% larger context window.
Speed Performance
| Metric | GPT-5 Codex | GPT-OSS-20b | Winner |
|---|---|---|---|
| Tokens/second | 314.7 tok/s | 307.3 tok/s | |
| Time to First Token | 10.95s | 0.52s |
Capabilities
Feature Comparison
| Feature | GPT-5 Codex | GPT-OSS-20b |
|---|---|---|
| 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-OSS-20b |
|---|---|---|
| License | Proprietary | Open Source |
| Author | OpenAI | OpenAI |
| Released | Sep 2025 | Aug 2025 |
GPT-5 Codex Modalities
Input
textimage
Output
text
GPT-OSS-20b Modalities
Input
text
Output
text