Grok 4 Fast
Grok 4 Fast (xAI) was released on Sep 19, 2025. In the Epoch AI capability ranking (ECI), it ranks #98 out of 267 models, with 144.19. On Arena, which measures human preference in blind comparisons, it has 1,437 ELO points (#145). Against models of the same generation, its best result is on Fiction.liveBench: 75.0%, #6 of 29.
Where Grok 4 Fast stands out and where it falls behind, by the numbers
Grok 4 Fast has published results on 8 tests compiled by Epoch AI. The yardstick here is its generation: its position among the models released between Dec 23, 2024 and Dec 18, 2025 that took the same test. Against the whole archive, which includes 2023 models, a recent release lands near the top of almost everything, and that says nothing.
Where it stands out
Tests where it sits in the top third of its own generation.
Where it falls behind
Tests where it sits in the bottom half of its own generation.
See all 8 tests, one by one
| Test | Score | In its generation | Overall | Test record |
|---|---|---|---|---|
| Dtbench | 82.7% | #11 / 47 (tied with 1) | #61 / 148 | 98.9% Claude Opus 5.5 |
| WeirdML | 42.9% | #21 / 41 | #65 / 112 | 93.6% GPT-6 Astra |
| ARC-AGI 2 | 5.3% | #15 / 36 | #56 / 83 | 95.0% GPT-6 Astra |
| WebDev Arena | 1,149 | #14 / 14 | #82 / 82 | 1,820 Claude Opus 5.5 |
| ARC-AGI | 48.5% | #16 / 35 | #58 / 81 | 98.5% Claude Fable 5 |
| ForecastBench | 60.50 | #16 / 28 | #23 / 62 | 62.50 o3 |
| Fiction.liveBench | 75.0% | #6 / 29 | #7 / 31 | 100.0% o3 |
| Cybench | 30.0% | #7 / 10 | #8 / 19 | 93.0% Claude Opus 4.6 |
For each test, the model's best effort level counts, as in the ranking. Source of the scores: Epoch AI, under CC BY 4.0.
What to compare Grok 4 Fast with
The models from other labs closest in capability and released in the same period, at most two per lab. Click any of them to see its page.
| Model | Lab | ECI | ELO | LiveBench | Release |
|---|---|---|---|---|---|
| Gemini 3.1 Flash-Lite | 144.47 | 1,460 | n/a | Mar 3, 2026 | |
| Gemini 2.5 Pro Exp (Mar 2025) | Google DeepMind | 144.20 | n/a | n/a | Mar 25, 2025 |
| Grok 4 Fast | xAI | 144.19 | 1,437 | n/a | Sep 19, 2025 |
| Qwen 3.6 35B-A3B | Alibaba | 144.11 | n/a | n/a | Apr 14, 2026 |
| Claude Opus 4.1 | Anthropic | 144.09 | 1,479 | n/a | Aug 5, 2025 |
| Qwen3-235B-A22B-Thinking-2507 | Alibaba | 143.88 | 1,483 | n/a | Jul 25, 2025 |
| GLM-4.7 | Z.ai (Zhipu AI) | 143.79 | 1,495 | n/a | Dec 22, 2025 |
Grok 4 Fast or Claude Opus 4.1?
Claude Opus 4.1 is the model from another lab closest to Grok 4 Fast in capability. Across the 5 tests both took, this is the score:
| Test | Grok 4 Fast | Claude Opus 4.1 |
|---|---|---|
| Cybench | 30.0% | 42.0% |
| WebDev Arena | 1,149 | 1,389 |
| WeirdML | 42.9% | 45.9% |
| Dtbench | 82.7% | 80.0% |
| ForecastBench | 60.50 | 62.00 |
Unweighted score: each test counts one point, whether math or coding. The dot marks who did better on each row.
Other models from xAI
The models from the same lab closest in time, newest first.
| Model | Release | ECI | ELO | LiveBench | Access |
|---|---|---|---|---|---|
| Grok 4.5 | Jul 8, 2026 | 153.93 | 1,495 | 75.8 | API access |
| Grok 4.3 (no thinking) | Apr 17, 2026 | 149.21 | 1,425 | 62.3 | Hosted access (no API) |
| Grok 4.3 Beta | Apr 17, 2026 | 148.95 | n/a | n/a | Hosted access (no API) |
| Grok 4.20 | Feb 17, 2026 | 152.08 | n/a | n/a | API access |
| Grok 4 Fast | Sep 19, 2025 | 144.19 | 1,437 | n/a | API access |
| Grok 4 | Jul 9, 2025 | 146.43 | n/a | n/a | API access |
| Grok-3 mini | Jun 24, 2025 | 140.33 | 1,394 | n/a | API access |
| Grok 3 | Apr 9, 2025 | 138.32 | n/a | n/a | API access |
| Grok-2 (Dec 2024) | Dec 12, 2024 | 130.49 | n/a | n/a | API access |
Have you used Grok 4 Fast? Rate it
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What people ask about Grok 4 Fast
Where does Grok 4 Fast rank among AI models?
In the ROO3 AI Benchmark, ordered by the Epoch AI ECI, Grok 4 Fast ranks #98 out of 267 models, with an ECI of 144.19. The ECI is a composite index that combines several hard benchmarks into a single scale. The position changes when a new model comes out, and the page is refreshed six times a day.
Is Grok 4 Fast better than Claude Opus 4.1?
Across the 5 tests both models took and Epoch AI compiled, Grok 4 Fast comes out ahead on 1, behind on 4 and tied on 0. It is a test-by-test count with no weighting: a win in math counts the same as a win in coding. To choose between the two, look at the tests that resemble your own use.
What is Grok 4 Fast best at?
Against models of the same generation (released up to 9 months before and up to 3 months after it), the best relative results of Grok 4 Fast are: Fiction.liveBench (#6 of 29); Dtbench (#11 of 47). The yardstick is its position among the models of that period that took the same test.
Where do the numbers on this page come from?
From the same three sources as the ranking, all openly licensed: Epoch AI (ECI and individual tests, CC BY 4.0), Arena (human-preference ELO, CC BY 4.0) and LiveBench (overall average, CC BY-SA 4.0). ROO3 does not measure any model. When the page shows a figure published by the maker itself, it appears in the written analysis, labeled as the maker's, and never enters the ranking.
Where each number comes from
Epoch AI, "AI Benchmarking Hub". Published at epoch.ai. Data under the CC BY 4.0 licence, reordered by roo3.co.
The Arena (LMArena) leaderboard, from the public lmarena-ai/leaderboard-dataset on Hugging Face, under the CC BY 4.0 licence. We are not affiliated with the Arena.
LiveBench, by the LiveBench team, published at livebench.ai under the CC BY-SA 4.0 license. The overall average is recomputed by roo3.co with the same formula as the website (average of the categories), and those numbers stay under CC BY-SA 4.0. We are not affiliated with LiveBench.
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