# GPT-5.3 Codex vs GPT-5.5

> Side-by-side benchmark comparison for GPT-5.3 Codex and GPT-5.5 across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-3-codex-vs-gpt-5-5
- Last updated: September 4, 2026

- Shared sourced benchmarks: 6
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Pick GPT-5.5 if you want the stronger benchmark profile. GPT-5.3 Codex only makes more sense when its price, context window, or workload-specific category wins matter more than the overall score.

## Summary

- GPT-5.5 leads overall 73.27 to 65.22.
- The clearest category separation is in reasoning, where the averages are 77.3 for GPT-5.3 Codex and 63.5 for GPT-5.5.
- The biggest single benchmark swing is Gert Labs in Agentic, with scores of 57.47% and 72.93%.
- GPT-5.3 Codex is the cheaper option on output tokens, which matters if you expect large responses or heavy interactive use.
- GPT-5.5 also has the larger context window at 1M.

## Model Snapshot

| Property | GPT-5.3 Codex | GPT-5.5 |
|----------|----------|----------|
| Creator | OpenAI | OpenAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 400K | 1M |
| Overall Score | 65.22 | 73.27 |
| Benchmarks Covered | 8 | 38 |
| Pricing (input/output) | $1.75 / $14.00 | $5.00 / $30.00 |

## Category Breakdown

### Agentic

- Winner: Coming soon
- GPT-5.3 Codex public-lane score: 62.3 (Estimated · #19/151)
- GPT-5.5 public-lane score: 63.9 (Supported · #15/151)

| Benchmark | GPT-5.3 Codex | GPT-5.5 | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.0 | 77.3% | 82% | GPT-5.5 |
| OSWorld-Verified | 64.7% | 78.7% | GPT-5.5 |
| Gert Labs | 57.47% | 72.93% | GPT-5.5 |
| JobBench | 33.7% | 42.7% | GPT-5.5 |
| CyberGym | Coming soon | 81.8% | Coming soon |
| BrowseComp | Coming soon | 84.4% | Coming soon |
| MCP Atlas | Coming soon | 75.3% | Coming soon |
| Toolathlon | Coming soon | 55.6% | Coming soon |
| τ²-bench results | Coming soon | 98% | Coming soon |
| ResearchClawBench | Coming soon | 17.0% | Coming soon |
| OSWorld 2.0 | Coming soon | 13.0% | Coming soon |
| ExploitGym | Coming soon | 13.4% | Coming soon |
| Terminal-Bench 2.1 (Vals) | Coming soon | 76.4% | Coming soon |

### Coding

- Winner: GPT-5.5
- GPT-5.3 Codex public-lane score: 62.7 (Supported · #16/183)
- GPT-5.5 public-lane score: 67.7 (Supported · #8/183)

| Benchmark | GPT-5.3 Codex | GPT-5.5 | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Verified | 85% | Coming soon | Coming soon |
| SWE-bench Pro | 56.8% | 58.6% | GPT-5.5 |
| SWE-Rebench | 58.2% | Coming soon | Coming soon |
| Vibe Code Bench | 61.77% | 69.85% | GPT-5.5 |
| Terminal-Bench 2.0 | Coming soon | 82.0% | Coming soon |
| React Native Evals | Coming soon | 84.7% | Coming soon |
| cursorBench31 | Coming soon | 59.2% | Coming soon |
| cursorBench32 | Coming soon | 58.4% | Coming soon |
| FrontierCode 1.1 Main | Coming soon | 43.0% | Coming soon |
| LiveCodeBench (Vals) | Coming soon | 85.3% | Coming soon |
| SWE-bench (Vals) | Coming soon | 82.6% | Coming soon |

### Multimodal & Grounded

- Winner: Coming soon
- GPT-5.3 Codex public-lane score: 75.6 (Unranked · 1 rankable row)
- GPT-5.5 public-lane score: 71.3 (#19/48)

| Benchmark | GPT-5.3 Codex | GPT-5.5 | Winner |
|-----------|-----------|-----------|--------|
| MMMU-Pro | Coming soon | 81.2% | Coming soon |
| MMMU-Pro w/ Python | Coming soon | 83.2% | Coming soon |
| OfficeQA Pro | Coming soon | 54.1% | Coming soon |

### Reasoning

- Winner: Coming soon
- GPT-5.3 Codex public-lane score: 77.3 (Unranked · 2 rankable rows)
- GPT-5.5 public-lane score: 63.5 (#15/22)

| Benchmark | GPT-5.3 Codex | GPT-5.5 | Winner |
|-----------|-----------|-----------|--------|
| MRCR v2 64K-128K | Coming soon | 83.1% | Coming soon |
| MRCR v2 128K-256K | Coming soon | 87.5% | Coming soon |
| ARC-AGI-2 | Coming soon | 85% | Coming soon |
| ARC-AGI-3 | Coming soon | 0.4% | Coming soon |

### Knowledge

- Winner: Coming soon
- GPT-5.3 Codex public-lane score: 66.3 (Estimated · #22/181)
- GPT-5.5 public-lane score: 73.3 (Supported · #7/181)

| Benchmark | GPT-5.3 Codex | GPT-5.5 | Winner |
|-----------|-----------|-----------|--------|
| GPQA | Coming soon | 93.6% | Coming soon |
| GPQA-D | Coming soon | 93.6% | Coming soon |
| HLE | Coming soon | 52.2% | Coming soon |
| HLE w/o tools | Coming soon | 41.4% | Coming soon |
| GPQA Diamond (Vals) | Coming soon | 93.2% | Coming soon |
| MMLU-Pro (Vals) | Coming soon | 88.1% | Coming soon |

### Instruction Following

- Winner: Coming soon
- GPT-5.3 Codex public-lane score: 92.3 (#15/120)
- GPT-5.5 public-lane score: 92.9 (#7/120)

### Mathematics

- Winner: Coming soon
- GPT-5.3 Codex public-lane score: Coming soon
- GPT-5.5 public-lane score: 69.6 (Unranked · 3 rankable rows)

| Benchmark | GPT-5.3 Codex | GPT-5.5 | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath (legacy) | Coming soon | 51.7% | Coming soon |
| FrontierMath v2 (Tiers 1-3) | Coming soon | 51.700% | Coming soon |
| FrontierMath v2 (Tier 4) | Coming soon | 35.400% | Coming soon |

## FAQ

### Which is better overall, GPT-5.3 Codex or GPT-5.5?

GPT-5.5 is ahead overall on BenchLM right now.

### Where is the biggest gap between GPT-5.3 Codex and GPT-5.5?

The widest category gap is in reasoning, where the averages are 77.3 for GPT-5.3 Codex and 63.5 for GPT-5.5.

### How many benchmarks does GPT-5.3 Codex cover on BenchLM?

GPT-5.3 Codex currently has 8 sourced benchmark scores on BenchLM.

### How many benchmarks does GPT-5.5 cover on BenchLM?

GPT-5.5 currently has 38 sourced benchmark scores on BenchLM.

## Related Comparisons

- [GPT-5.3 Codex vs GPT-5.3-Codex-Spark](/compare/gpt-5-3-codex-vs-gpt-5-3-codex-spark)
- [GPT-5.5 vs GPT-5.3-Codex-Spark](/compare/gpt-5-3-codex-spark-vs-gpt-5-5)
- [GPT-5.3 Codex vs GPT-5.5 Pro](/compare/gpt-5-3-codex-vs-gpt-5-5-pro)
- [GPT-5.5 vs GPT-5.5 Pro](/compare/gpt-5-5-vs-gpt-5-5-pro)

## Explore More

- [GPT-5.3 Codex profile](/models/gpt-5-3-codex)
- [GPT-5.5 profile](/models/gpt-5-5)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)