# GPT-5.3 Codex vs o3-pro

> GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 42.9 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-3-codex-vs-o3-pro
- Last updated: 2026-10-11
- Shared benchmarks: 2

## Summary

- They share 2 benchmarks with published results for both. GPT-5.3 Codex scores higher in 0 categories and o3-pro in 1 category; one gap is clear of the uncertainty.
- The widest gap is in coding, where o3-pro leads 55.5 to 48.6.
- The biggest single-benchmark swing is WeirdML: 79.3% for GPT-5.3 Codex and 58.2% for o3-pro.
- GPT-5.3 Codex is cheaper at $1.75 / $14 per million input/output tokens, against $20 / $80 for o3-pro.
- GPT-5.3 Codex accepts more context: 400K tokens versus 200K.

## Snapshot

| | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 45.8 | 42.9 |
| Rank | 69 | 105 |
| Context | 400K | 200K |
| Input $/M | $1.75 | $20 |
| Output $/M | $14 | $80 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.3 Codex: 48.6 (#56)
- o3-pro: 55.5 (#24)

| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| WeirdML | 79.3% | 58.2% |
| SWE-bench Verified | 74.8% | — |
| Aider Polyglot | — | 84.9% |
| LMArena WebDev | 1409 | — |
| ALE-Bench | 1,655 | — |

## Agentic & Tool Use

- GPT-5.3 Codex: 48.0 (#9)
- o3-pro: —

| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Terminal-Bench | 78.4% | — |
| METR Time Horizons | 74.5% | — |
| Vending-Bench 2 | 5,940 | — |

## Reasoning

- GPT-5.3 Codex: —
- o3-pro: 23.8 (#171)

| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Epoch Capabilities Index | 156.77 | 147.42 |
| ARC-AGI-2 | — | 4.9% |
| Kagi LLM Benchmark | — | 72.1% |
| ARC-AGI-1 | — | 59.3% |
| DTBench | — | 86.9% |
| LMCA | — | 38.5% |

## Knowledge

- GPT-5.3 Codex: —
- o3-pro: 29.5 (#238)

| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Confabulations | — | 14.2% |
| Vectara Hallucination Rate | — | 23.3% |

## Long Context

- GPT-5.3 Codex: —
- o3-pro: 72.2 (#1)

| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Fiction.LiveBench | — | 97.2% |

## Writing & Preference

- GPT-5.3 Codex: —
- o3-pro: 57.1 (#133)

| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Short-Story Creative Writing | — | 84.4% |

## FAQ

### Is GPT-5.3 Codex better than o3-pro?

GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 42.9 on the Noometry Index.

### Which is cheaper, GPT-5.3 Codex or o3-pro?

GPT-5.3 Codex is cheaper. It lists at $1.75 per million input tokens and $14 per million output tokens; o3-pro lists at $20 and $80.

### Is GPT-5.3 Codex or o3-pro better for coding?

o3-pro scores higher on coding benchmarks: 55.5 versus 48.6 in the Noometry coding category.

### Which has the bigger context window?

GPT-5.3 Codex does, with 400K tokens against 200K.

### How many benchmarks do GPT-5.3 Codex and o3-pro share?

2 benchmarks have published results for both models. GPT-5.3 Codex has 8 scored results on Noometry and o3-pro has 12.