Model comparison
GPT-5-Codex vs Mercury
GPT-5-Codex and Mercury score almost the same on the Noometry Index (37.9 vs 37.6), so choose on price, context window or the category you care about most.
Last verified . 1 shared benchmarks.
Summary
- They share 1 benchmark with published results for both. GPT-5-Codex scores higher in 2 categories and Mercury in 0 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5-Codex leads 30.9 to 17.5.
- The biggest single-benchmark swing is Kagi LLM Benchmark: 70.3% for GPT-5-Codex and 21.6% for Mercury.
Side by side
| GPT-5-Codex | Mercury | |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 37.9 | 37.6 |
| Released | 2025-09-15 | — |
| Weights | Proprietary | Proprietary |
| Context window | 400K | — |
| Max output | 128K | — |
| Input $ / M tokens | $1.25 | — |
| Output $ / M tokens | $10 | — |
| Results tracked | 3 | 9 |
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Category by category
Coding GPT-5-Codex leads
GPT-5-Codex: 42.4 (#103), Mercury: 38.7 (#170)
| Benchmark | GPT-5-Codex | Mercury |
|---|---|---|
| WeirdML | 54.5% | — |
| LMArena Coding | — | 1322 |
Agentic & Tool Use Not comparable
GPT-5-Codex: 31.0 (#72), Mercury: —
| Benchmark | GPT-5-Codex | Mercury |
|---|---|---|
| Terminal-Bench | 44.3% | — |
Reasoning GPT-5-Codex leads
GPT-5-Codex: 30.9 (#83), Mercury: 17.5 (#293)
| Benchmark | GPT-5-Codex | Mercury |
|---|---|---|
| Kagi LLM Benchmark | 70.3% | 21.6% |
| LMArena Hard Prompts | — | 1285 |
Multilingual Not comparable
GPT-5-Codex: —, Mercury: 41.6 (#206)
| Benchmark | GPT-5-Codex | Mercury |
|---|---|---|
| LMArena Non-English | — | 1260 |
Instruction Following Not comparable
GPT-5-Codex: —, Mercury: 65.2 (#224)
| Benchmark | GPT-5-Codex | Mercury |
|---|---|---|
| LMArena Instruction Following | — | 1239 |
Long Context Not comparable
GPT-5-Codex: —, Mercury: 38.4 (#198)
| Benchmark | GPT-5-Codex | Mercury |
|---|---|---|
| LMArena Longer Query | — | 1266 |
Writing & Preference Not comparable
GPT-5-Codex: —, Mercury: 46.2 (#221)
| Benchmark | GPT-5-Codex | Mercury |
|---|---|---|
| LMArena Text | — | 1282 |
| LMArena Creative Writing | — | 1191 |
| LMArena Multi-Turn | — | 1282 |
Frequently asked questions
Is GPT-5-Codex better than Mercury?
GPT-5-Codex and Mercury score almost the same on the Noometry Index (37.9 vs 37.6), so choose on price, context window or the category you care about most.
Is GPT-5-Codex or Mercury better for coding?
GPT-5-Codex scores higher on coding benchmarks: 42.4 versus 38.7 in the Noometry coding category.
How many benchmarks do GPT-5-Codex and Mercury share?
1 benchmark has published results for both models. GPT-5-Codex has 3 scored results on Noometry and Mercury has 9.