# GPT-5.3 Codex vs Mercury

> GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 37.6 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-3-codex-vs-mercury
- Last updated: 2026-10-11
- Shared benchmarks: 0

## Summary

- The widest gap is in coding, where GPT-5.3 Codex leads 48.6 to 38.7.

## Snapshot

| | GPT-5.3 Codex | Mercury |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 45.8 | 37.6 |
| Rank | 69 | 199 |
| Context | 400K | — |
| Input $/M | $1.75 | — |
| Output $/M | $14 | — |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.3 Codex: 48.6 (#56)
- Mercury: 38.7 (#170)

| Benchmark | GPT-5.3 Codex | Mercury |
|---|---|---|
| SWE-bench Verified | 74.8% | — |
| LMArena WebDev | 1409 | — |
| WeirdML | 79.3% | — |
| LMArena Coding | — | 1322 |
| ALE-Bench | 1,655 | — |

## Agentic & Tool Use

- GPT-5.3 Codex: 48.0 (#9)
- Mercury: —

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

## Reasoning

- GPT-5.3 Codex: —
- Mercury: 17.5 (#293)

| Benchmark | GPT-5.3 Codex | Mercury |
|---|---|---|
| Kagi LLM Benchmark | — | 21.6% |
| LMArena Hard Prompts | — | 1285 |
| Epoch Capabilities Index | 156.77 | — |

## Multilingual

- GPT-5.3 Codex: —
- Mercury: 41.6 (#206)

| Benchmark | GPT-5.3 Codex | Mercury |
|---|---|---|
| LMArena Non-English | — | 1260 |

## Instruction Following

- GPT-5.3 Codex: —
- Mercury: 65.2 (#224)

| Benchmark | GPT-5.3 Codex | Mercury |
|---|---|---|
| LMArena Instruction Following | — | 1239 |

## Long Context

- GPT-5.3 Codex: —
- Mercury: 38.4 (#198)

| Benchmark | GPT-5.3 Codex | Mercury |
|---|---|---|
| LMArena Longer Query | — | 1266 |

## Writing & Preference

- GPT-5.3 Codex: —
- Mercury: 46.2 (#221)

| Benchmark | GPT-5.3 Codex | Mercury |
|---|---|---|
| LMArena Text | — | 1282 |
| LMArena Creative Writing | — | 1191 |
| LMArena Multi-Turn | — | 1282 |

## FAQ

### Is GPT-5.3 Codex better than Mercury?

GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 37.6 on the Noometry Index.

### Is GPT-5.3 Codex or Mercury better for coding?

GPT-5.3 Codex scores higher on coding benchmarks: 48.6 versus 38.7 in the Noometry coding category.

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

0 benchmarks have published results for both models. GPT-5.3 Codex has 8 scored results on Noometry and Mercury has 9.