Model comparison
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.
Last verified . 0 shared benchmarks.
Summary
- The widest gap is in coding, where GPT-5.3 Codex leads 48.6 to 38.7.
Side by side
| GPT-5.3 Codex | Mercury | |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 45.8 | 37.6 |
| Released | 2026-02-05 | — |
| Weights | Proprietary | Proprietary |
| Context window | 400K | — |
| Max output | 128K | — |
| Input $ / M tokens | $1.75 | — |
| Output $ / M tokens | $14 | — |
| Results tracked | 8 | 9 |
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Category by category
Coding GPT-5.3 Codex leads
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 Not comparable
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 Not comparable
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 Not comparable
GPT-5.3 Codex: —, Mercury: 41.6 (#206)
| Benchmark | GPT-5.3 Codex | Mercury |
|---|---|---|
| LMArena Non-English | — | 1260 |
Instruction Following Not comparable
GPT-5.3 Codex: —, Mercury: 65.2 (#224)
| Benchmark | GPT-5.3 Codex | Mercury |
|---|---|---|
| LMArena Instruction Following | — | 1239 |
Long Context Not comparable
GPT-5.3 Codex: —, Mercury: 38.4 (#198)
| Benchmark | GPT-5.3 Codex | Mercury |
|---|---|---|
| LMArena Longer Query | — | 1266 |
Writing & Preference Not comparable
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 |
Frequently asked questions
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.