# Grok 4.20 vs Grok 4 Fast (Reasoning)

> Side-by-side benchmark comparison for Grok 4.20 and Grok 4 Fast (Reasoning) across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/grok-4-20-beta-vs-grok-4-fast-reasoning
- Last updated: September 10, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Evidence is too thin for a benchmark verdict: Grok 4.20 and Grok 4 Fast (Reasoning) share only 1 sourced benchmark row.

## Summary

- Only 1 shared sourced benchmark row is available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.

## Model Snapshot

| Property | Grok 4.20 | Grok 4 Fast (Reasoning) |
|----------|----------|----------|
| Creator | xAI | xAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 2M | 2M |
| Independent public score (not head-to-head) | 67.13 | 51.31 |
| Benchmarks Covered | 23 | 1 |
| Pricing (input/output) | $2.00 / $6.00 | N/A |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Grok 4.20 public-lane score: 26.7 (Supported · #145/152)
- Grok 4 Fast (Reasoning) public-lane score: Coming soon

| Benchmark | Grok 4.20 | Grok 4 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.0 | 47.1% | Coming soon | Coming soon |
| DeepSearchQA | 62.8% | Coming soon | Coming soon |
| Gert Labs | 38.36% | Coming soon | Coming soon |
| Terminal-Bench 2.1 (Vals) | 44.2% | Coming soon | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Grok 4.20 public-lane score: 28.2 (Supported · #141/151)
- Grok 4 Fast (Reasoning) public-lane score: 41.1 (Estimated · #110/151)

| Benchmark | Grok 4.20 | Grok 4 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| LiveCodeBench Pro | 74.2% | Coming soon | Coming soon |
| SWE-bench Verified | 76.7% | Coming soon | Coming soon |
| SWE-bench Pro | 51.8% | Coming soon | Coming soon |
| Vibe Code Bench | 4.06% | 0.00% | Grok 4.20 |
| LiveCodeBench (Vals) | 84.3% | Coming soon | Coming soon |
| SWE-bench (Vals) | 72.2% | Coming soon | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Grok 4.20 public-lane score: 34.6 (#43/48)
- Grok 4 Fast (Reasoning) public-lane score: 51.1 (Unranked · 1 rankable row)

| Benchmark | Grok 4.20 | Grok 4 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| MMMU-Pro | 75.2% | Coming soon | Coming soon |
| CharXiv | 60.9% | Coming soon | Coming soon |
| ERQA | 54.1% | Coming soon | Coming soon |
| SimpleVQA | 57.4% | Coming soon | Coming soon |
| MedXpertQA (MM) | 65.8% | Coming soon | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- Grok 4.20 public-lane score: 34.2 (Unranked · 2 rankable rows)
- Grok 4 Fast (Reasoning) public-lane score: 71.7 (Unranked · 2 rankable rows)

| Benchmark | Grok 4.20 | Grok 4 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-2 | 53.3% | Coming soon | Coming soon |
| ARC-AGI-3 | 0.1% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Grok 4.20 public-lane score: 49.4 (Supported · #85/183)
- Grok 4 Fast (Reasoning) public-lane score: 47.1 (Estimated · #99/183)

| Benchmark | Grok 4.20 | Grok 4 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| GPQA-D | 88.5% | Coming soon | Coming soon |
| HLE w/o tools | 31.6% | Coming soon | Coming soon |
| HealthBench Hard | 20.3% | Coming soon | Coming soon |
| MedXpertQA (Text) | 50.2% | Coming soon | Coming soon |
| GPQA Diamond (Vals) | 88.6% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 86.3% | Coming soon | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Grok 4.20 public-lane score: Coming soon
- Grok 4 Fast (Reasoning) public-lane score: 60.3 (#72/123)

## FAQ

### Is there enough evidence to pick between Grok 4.20 and Grok 4 Fast (Reasoning)?

Not yet. The models share only 1 sourced benchmark row, so this mirror reports the available measurements and metadata without naming a broad winner.

### What can I compare safely on this page?

Published pricing, context windows, model type, and individual shared benchmark rows are directly comparable. Independent overall scores and non-overlapping benchmark coverage are labeled separately and should not be read as a controlled head-to-head result.

## Related Comparisons

- [Grok 4.20 vs Grok 4.20 Multi-agent](/compare/grok-4-20-beta-vs-grok-4-20-multi-agent-beta)
- [Grok 4 Fast (Reasoning) vs Grok 4.20 Multi-agent](/compare/grok-4-20-multi-agent-beta-vs-grok-4-fast-reasoning)
- [Grok 4.20 vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-grok-4-20-beta)
- [Grok 4 Fast (Reasoning) vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-grok-4-fast-reasoning)

## Explore More

- [Grok 4.20 profile](/models/grok-4-20-beta)
- [Grok 4 Fast (Reasoning) profile](/models/grok-4-fast-reasoning)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)