# GPT-5.3 Codex vs gpt-oss-120b

> GPT-5.3 Codex is the stronger model overall, scoring 45.5 to 36.0 on the Noometry Index. gpt-oss-120b costs 69× less per token, which makes it the better buy when GPT-5.3 Codex's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/gpt-5-3-codex-vs-gpt-oss-120b
- Last updated: 2026-10-10
- Shared benchmarks: 6

## Summary

- They share 6 benchmarks with published results for both. GPT-5.3 Codex scores higher in 2 categories and gpt-oss-120b in 0 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in agentic & tool use, where GPT-5.3 Codex leads 47.8 to 12.1.
- The biggest single-benchmark swing is Terminal-Bench: 78.4% for GPT-5.3 Codex and 18.7% for gpt-oss-120b.
- gpt-oss-120b is cheaper at $0.037 / $0.17 per million input/output tokens, against $1.75 / $14 for GPT-5.3 Codex.
- GPT-5.3 Codex accepts more context: 400K tokens versus 131K.
- gpt-oss-120b has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 45.5 | 36.0 |
| Rank | 61 | 210 |
| Context | 400K | 131K |
| Input $/M | $1.75 | $0.037 |
| Output $/M | $14 | $0.17 |
| Weights | Proprietary | Open |

## Coding

- GPT-5.3 Codex: 48.5 (#51)
- gpt-oss-120b: 33.2 (#251)

| Benchmark | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| WeirdML | 79.3% | 48.2% |
| ALE-Bench | 1,655 | 575.62 |
| SWE-bench Verified | 74.8% | — |
| SWE-bench Verified (bash only) | — | 26% |
| Aider Polyglot | — | 41.8% |
| LMArena WebDev | 1408 | — |
| SciCode | — | 36% |
| LMArena Coding | — | 1380 |
| AlgoTune | — | 1.41 |

## Agentic & Tool Use

- GPT-5.3 Codex: 47.8 (#9)
- gpt-oss-120b: 12.1 (#145)

| Benchmark | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| Terminal-Bench | 78.4% | 18.7% |
| METR Time Horizons | 74.5% | 56.6% |
| Vending-Bench 2 | 5,940 | -21.53 |
| APEX-Agents | — | 4.4% |

## Reasoning

- GPT-5.3 Codex: —
- gpt-oss-120b: 19.5 (#236)

| Benchmark | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| Epoch Capabilities Index | 156.84 | 139.94 |
| SimpleBench | — | 22.1% |
| Kagi LLM Benchmark | — | 58.6% |
| CritPt | — | 1.1% |
| Chess Puzzles | — | 20% |
| LMArena Hard Prompts | — | 1364 |
| Mystery Game Puzzles | — | 2% |
| DTBench | — | 76.3% |
| LMCA | — | 22.1% |
| Surface Evolver Bench | — | 25% |

## Math

- GPT-5.3 Codex: —
- gpt-oss-120b: 50.6 (#43)

| Benchmark | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| OTIS Mock AIME 2024-2025 | — | 88.9% |
| Omni-MATH | — | 68.8% |
| LMArena Math | — | 1388 |

## Knowledge

- GPT-5.3 Codex: —
- gpt-oss-120b: 42.3 (#89)

| Benchmark | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| GPQA Diamond | — | 75.8% |
| MMLU-Pro | — | 79.5% |
| Confabulations | — | 15.7% |
| Vectara Hallucination Rate | — | 14.2% |
| GPQA (HELM) | — | 68.4% |
| LMArena Expert | — | 1356 |

## Multilingual

- GPT-5.3 Codex: —
- gpt-oss-120b: 48.2 (#142)

| Benchmark | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| LMArena Non-English | — | 1350 |
| LMArena Chinese | — | 1384 |
| LMArena French | — | 1370 |
| LMArena German | — | 1355 |
| LMArena Japanese | — | 1332 |
| LMArena Korean | — | 1283 |
| LMArena Russian | — | 1343 |
| LMArena Spanish | — | 1388 |

## Instruction Following

- GPT-5.3 Codex: —
- gpt-oss-120b: 69.5 (#168)

| Benchmark | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| IFEval | — | 83.6% |
| LMArena Instruction Following | — | 1318 |

## Long Context

- GPT-5.3 Codex: —
- gpt-oss-120b: 31.4 (#273)

| Benchmark | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| Fiction.LiveBench | — | 44.4% |
| LMArena Longer Query | — | 1319 |

## Writing & Preference

- GPT-5.3 Codex: —
- gpt-oss-120b: 46.7 (#213)

| Benchmark | GPT-5.3 Codex | gpt-oss-120b |
|---|---|---|
| LMArena Text | — | 1366 |
| LMArena Creative Writing | — | 1274 |
| Short-Story Creative Writing | — | 77.1% |
| EQ-Bench Creative Writing | — | 961 |
| WildBench | — | 84.5% |
| LMArena Multi-Turn | — | 1340 |

## FAQ

### Is GPT-5.3 Codex better than gpt-oss-120b?

GPT-5.3 Codex is the stronger model overall, scoring 45.5 to 36.0 on the Noometry Index. gpt-oss-120b costs 69× less per token, which makes it the better buy when GPT-5.3 Codex's lead doesn't matter for your workload.

### Which is cheaper, GPT-5.3 Codex or gpt-oss-120b?

gpt-oss-120b is cheaper. It lists at $0.037 per million input tokens and $0.17 per million output tokens; GPT-5.3 Codex lists at $1.75 and $14.

### Is GPT-5.3 Codex or gpt-oss-120b better for coding?

GPT-5.3 Codex scores higher on coding benchmarks: 48.5 versus 33.2 in the Noometry coding category.

### Which has the bigger context window?

GPT-5.3 Codex does, with 400K tokens against 131K.

### How many benchmarks do GPT-5.3 Codex and gpt-oss-120b share?

6 benchmarks have published results for both models. GPT-5.3 Codex has 8 scored results on Noometry and gpt-oss-120b has 48.