GPT-5.3 Codex vs GPT-5.5 Pro
GPT-5.3 Codex Verdict
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 65.4.
- GPT-5.3 Codex (xhigh) is stronger in agents & tools, coding, composite, instruction following, knowledge, long context, multimodal.
- GPT-5.5 Pro (xhigh) is stronger in reasoning, maths.
- GPT-5.3 Codex (xhigh) is 14× cheaper ($4.81 vs $67.50 per 1M blended).
- GPT-5.3 Codex (xhigh) streams 31.2× faster (125 vs 4 tokens per second).
| Metric | GPT-5.3 Codex (xhigh) | GPT-5.5 Pro (xhigh) |
|---|---|---|
| BenchLeader Index | 65.4 | 67.1 |
| Agents & tools score | 79.8 | – |
| Coding score | 61.7 | – |
| Composite score | 70.2 | – |
| Instruction following score | 73.4 | – |
| Knowledge score | 69.4 | – |
| Long context score | 68.2 | – |
| Multimodal score | 63.0 | – |
| Reasoning score | 74.4 | 80.1 |
| Maths score | – | 74.5 |
| Blended price $/M | $4.81 | $67.50 |
| Output speed | 125 tok/s | 4 tok/s |
| Time to first answer | 50.8 s | 3.5 s |
| Context window | 400k | 1.1M |
| FrontierMath Tiers 1–3 | – | 87.7% |
| FrontierMath Tier 4 | – | 78.0% |
| WeirdML | 77.9% | – |
| AA Intelligence Index | 32.5 | – |
| IFBench | 75.4% | – |
| AA-LCR | 83.3% | – |
| MMMU-Pro | 78.5% | – |
| AA-Omniscience | 10.9 | – |
| Terminal-Bench Hard | 53.0% | – |
| GPQA Diamond (AA) | 91.5% | – |
| Humanity's Last Exam (AA) | 42.5% | – |
| τ²-Bench Telecom (AA) | 86.0% | – |
| LiveCodeBench | 87.3% | – |
| IOI | 53.8% | – |
| SWE-bench (Vals) | 78.0% | – |
| ARC-AGI-1 | – | 95.0% |
| ARC-AGI-2 | – | 84.2% |
| CritPt | 16.9% | 30.6% |
| Vibe Code Bench v1.1 | 61.8% | – |
| LMCA | – | 53.9% |
| DTBench | – | 96.0% |
| ALE-Bench | 1655.2 | – |
Data as of 2026-09-19. Best configuration of each model; every score links to its source on the model pages.
GPT-5.3 Codex vs GPT-5.5 Pro: questions
- Is GPT-5.3 Codex better than GPT-5.5 Pro?
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 65.4. The BenchLeader Index combines every independent quality benchmark; GPT-5.5 Pro (xhigh) is ahead overall as of 2026-09-19, but check the category scores for your use.
- Which is cheaper, GPT-5.3 Codex or GPT-5.5 Pro?
- GPT-5.3 Codex is cheaper: $4.81 against $67.50 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.3 Codex or GPT-5.5 Pro?
- GPT-5.3 Codex streams faster: 125 against 4 output tokens per second.
- Which has the larger context window?
- GPT-5.5 Pro accepts more context: 1.1M against 400k tokens.