Model comparison
Grok 4 Fast vs Mercury
Grok 4 Fast is the stronger model overall, scoring 39.4 to 37.6 on the Noometry Index.
Last verified . 9 shared benchmarks.
Summary
- They share 9 benchmarks with published results for both. Grok 4 Fast scores higher in 5 categories and Mercury in 1 category; 6 gaps are clear of the uncertainty.
- The widest gap is in long context, where Grok 4 Fast leads 63.2 to 38.4.
- The biggest single-benchmark swing is Kagi LLM Benchmark: 66.1% for Grok 4 Fast and 21.6% for Mercury.
Side by side
| Grok 4 Fast | Mercury | |
|---|---|---|
| Provider | xAI | Inception |
| Noometry Index | 39.4 | 37.6 |
| Released | 2025-09-19 | — |
| Weights | Proprietary | Proprietary |
| Context window | — | — |
| Max output | — | — |
| Input $ / M tokens | — | — |
| Output $ / M tokens | — | — |
| Results tracked | 30 | 9 |
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Category by category
Coding Mercury leads
Grok 4 Fast: 32.5 (#271), Mercury: 38.7 (#170)
| Benchmark | Grok 4 Fast | Mercury |
|---|---|---|
| LMArena Coding | 1429 | 1322 |
| LMArena WebDev | 1159 | — |
| WeirdML | 42.9% | — |
Agentic & Tool Use Not comparable
Grok 4 Fast: 29.5 (#86), Mercury: —
| Benchmark | Grok 4 Fast | Mercury |
|---|---|---|
| τ²-bench Banking | 15.7% | — |
| Cybench | 30% | — |
| LMArena Search | 1171 | — |
Reasoning Grok 4 Fast leads
Grok 4 Fast: 22.2 (#201), Mercury: 17.5 (#293)
| Benchmark | Grok 4 Fast | Mercury |
|---|---|---|
| Kagi LLM Benchmark | 66.1% | 21.6% |
| LMArena Hard Prompts | 1412 | 1285 |
| ARC-AGI-2 | 5.3% | — |
| ARC-AGI-1 | 48.5% | — |
| DTBench | 82.7% | — |
| Epoch Capabilities Index | 144.2 | — |
| ForecastBench | 60.5 | — |
Math Not comparable
Grok 4 Fast: 38.9 (#123), Mercury: —
| Benchmark | Grok 4 Fast | Mercury |
|---|---|---|
| LMArena Math | 1419 | — |
Knowledge Not comparable
Grok 4 Fast: 32.0 (#214), Mercury: —
| Benchmark | Grok 4 Fast | Mercury |
|---|---|---|
| Vectara Hallucination Rate | 19.7% | — |
| LMArena Expert | 1411 | — |
Multilingual Grok 4 Fast leads
Grok 4 Fast: 51.3 (#111), Mercury: 41.6 (#206)
| Benchmark | Grok 4 Fast | Mercury |
|---|---|---|
| LMArena Non-English | 1396 | 1260 |
| LMArena Chinese | 1457 | — |
| LMArena French | 1431 | — |
| LMArena German | 1383 | — |
| LMArena Japanese | 1352 | — |
| LMArena Korean | 1357 | — |
| LMArena Russian | 1389 | — |
| LMArena Spanish | 1415 | — |
Instruction Following Grok 4 Fast leads
Grok 4 Fast: 73.2 (#121), Mercury: 65.2 (#224)
| Benchmark | Grok 4 Fast | Mercury |
|---|---|---|
| LMArena Instruction Following | 1387 | 1239 |
Long Context Grok 4 Fast leads
Grok 4 Fast: 63.2 (#3), Mercury: 38.4 (#198)
| Benchmark | Grok 4 Fast | Mercury |
|---|---|---|
| LMArena Longer Query | 1415 | 1266 |
| Fiction.LiveBench | 94.4% | — |
Writing & Preference Grok 4 Fast leads
Grok 4 Fast: 60.0 (#102), Mercury: 46.2 (#221)
| Benchmark | Grok 4 Fast | Mercury |
|---|---|---|
| LMArena Text | 1407 | 1282 |
| LMArena Creative Writing | 1387 | 1191 |
| LMArena Multi-Turn | 1414 | 1282 |
Frequently asked questions
Is Grok 4 Fast better than Mercury?
Grok 4 Fast is the stronger model overall, scoring 39.4 to 37.6 on the Noometry Index.
Is Grok 4 Fast or Mercury better for coding?
Mercury scores higher on coding benchmarks: 38.7 versus 32.5 in the Noometry coding category.
How many benchmarks do Grok 4 Fast and Mercury share?
9 benchmarks have published results for both models. Grok 4 Fast has 30 scored results on Noometry and Mercury has 9.