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Gemini 3 Flash Preview vs Grok 4.20

Updated October 21, 2026. 46 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace Gemini 3 Flash Preview Replace Grok 4.20
Gemini 3 Flash PreviewGoogle
Coding
43.7
Overall
26.3
Output $/M
$3.00
30
Grok 4.20xAI
Coding
33.3
Overall
25.7
Output $/M
$2.50
15
vs boards won of 46 shared, 1 tied

Decision reading

Pick Gemini 3 Flash Preview for coding: it scores 43.7 on the Vibe Coding Index against 33.3 for Grok 4.20.

Pick Grok 4.20 when output tokens cost 1.2x less, or when the context window is larger, 2M against 1.05M tokens.

Model AGemini 3 Flash PreviewGoogle43.7/1002 independent benchmarks$0.37 per solved taskModel BGrok 4.20xAI33.3/1002 independent benchmarks$0.72 per solved task
Shared results
46
Gemini 3 Flash Preview only
23
Grok 4.20 only
8
Like-for-like categories
8 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

At a glance

Coding index
Gemini 3 Flash Preview 43.7 from 2 benchmarks, Grok 4.20 33.3 from 2 benchmarks.
Widest category
Knowledge, 8.0 points apart on average over 8 shared benchmarks.
Widest single gap
ARC-AGI-2: Gemini 3 Flash Preview 33.6% against Grok 4.20 65.1%, 31.5 points apart on a 0 to 100 scale.
Output price
Gemini 3 Flash Preview $3.00 against Grok 4.20 $2.50 per million output tokens, 1.2x apart.
Context window
Gemini 3 Flash Preview takes 1.05M tokens, Grok 4.20 2M.

Benchmark by benchmark

First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.

Boards won, where both have a result
CategoryGemini 3 Flash PreviewBarsGrok 4.20Ties
Coding80
Intelligence10
Agentic work731 tie
Reasoning24
Math01
Knowledge71
Web design04
General52
All shared boards30151 tie
CodingLike-for-likeSix of these boards feed the Vibe Coding Index80
Coding benchmarks for Gemini 3 Flash Preview and Grok 4.20
BenchmarkGemini 3 Flash PreviewGrok 4.20Leader
SWE-bench Verified75.8%Not measuredOnly Gemini 3 Flash Preview measured
LiveCodeBench (Vals AI)85.6%84.3%Gemini 3 Flash Preview
SWE-bench Verified (Vals AI)75.0%72.2%Gemini 3 Flash Preview
Vibe Code Bench (Vals AI)20.2%4.1%Gemini 3 Flash Preview
Code migration (Vals AI)6.4%0.3%Gemini 3 Flash Preview
ProgramBench (Vals AI)0.0%Not measuredOnly Gemini 3 Flash Preview measured
Terminal-Bench 2.1 (Vals AI)53.9%44.2%Gemini 3 Flash Preview
LiveCodeBench (Artificial Analysis run)90.8%Not measuredOnly Gemini 3 Flash Preview measured
Terminal-Bench Hard (Artificial Analysis run)38.6%37.9%Gemini 3 Flash Preview
Terminal-Bench64.3%57.3%Gemini 3 Flash Preview
GSO-Bench9.8%Not measuredOnly Gemini 3 Flash Preview measured
WeirdML61.6%52.3%Gemini 3 Flash Preview
ALE-Bench1367.2Not measuredOnly Gemini 3 Flash Preview measured
Neither model has a result on the other 25 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
Intelligence benchmarks for Gemini 3 Flash Preview and Grok 4.20
BenchmarkGemini 3 Flash PreviewGrok 4.20Leader
AA Intelligence Index26.325.7Gemini 3 Flash Preview
Epoch Capabilities IndexNot measured152.1Only Grok 4.20 measured
Agentic workLike-for-likePublic boards, shown as published, kept out of the index73
Agentic work benchmarks for Gemini 3 Flash Preview and Grok 4.20
BenchmarkGemini 3 Flash PreviewGrok 4.20Leader
Design Arena: agents building web apps11101144Grok 4.20
Design Arena: agents building full-stack apps10631054Gemini 3 Flash Preview
Design Arena: agents building mobile apps10901090Tie
Design Arena: agents building Android apps10571052Gemini 3 Flash Preview
Design Arena: agents building Godot games11611089Gemini 3 Flash Preview
Design Arena: HTML slidesNot measured1180Only Grok 4.20 measured
Design Arena: PowerPoint slides1036Not measuredOnly Gemini 3 Flash Preview measured
Finance Agent (Vals AI)42.5%28.5%Gemini 3 Flash Preview
Tax Agent Bench (Vals AI)11.8%7.0%Gemini 3 Flash Preview
Legal Research Bench (Vals AI)18.3%13.9%Gemini 3 Flash Preview
Excel Modeling Benchmark (Vals AI)26.0%11.7%Gemini 3 Flash Preview
τ²-Bench Telecom80.4%93.0%Grok 4.20
BALROG48.1%Not measuredOnly Gemini 3 Flash Preview measured
DeepResearch Bench49.8%Not measuredOnly Gemini 3 Flash Preview measured
Vending-Bench 2$3,635$4,663Grok 4.20
Neither model has a result on the other 24 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index24
Reasoning benchmarks for Gemini 3 Flash Preview and Grok 4.20
BenchmarkGemini 3 Flash PreviewGrok 4.20Leader
GPQA Diamond87.9%88.6%Grok 4.20
MMMU Pro (Vals AI)87.6%83.5%Gemini 3 Flash Preview
GPQA Diamond (Artificial Analysis run)89.8%91.1%Grok 4.20
Humanity's Last Exam (Artificial Analysis run)36.6%34.5%Gemini 3 Flash Preview
GPQA Diamond (Epoch AI run)89.4%Not measuredOnly Gemini 3 Flash Preview measured
ARC-AGI84.7%89.5%Grok 4.20
ARC-AGI-233.6%65.1%Grok 4.20
SimpleBench61.1%Not measuredOnly Gemini 3 Flash Preview measured
Chess puzzles39.0%Not measuredOnly Gemini 3 Flash Preview measured
Mystery game puzzles26.0%Not measuredOnly Gemini 3 Flash Preview measured
VPCT72.6%Not measuredOnly Gemini 3 Flash Preview measured
Neither model has a result on the other 10 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index01
Math benchmarks for Gemini 3 Flash Preview and Grok 4.20
BenchmarkGemini 3 Flash PreviewGrok 4.20Leader
AIME95.6%96.5%Grok 4.20
MGSM (Vals AI)93.3%Not measuredOnly Gemini 3 Flash Preview measured
AA Math Index97.0Not measuredOnly Gemini 3 Flash Preview measured
AIME 2025 (Artificial Analysis run)97.0%Not measuredOnly Gemini 3 Flash Preview measured
OTIS Mock AIME95.6%Not measuredOnly Gemini 3 Flash Preview measured
FrontierMath, tiers 1 to 351.2%Not measuredOnly Gemini 3 Flash Preview measured
FrontierMath, tier 417.1%Not measuredOnly Gemini 3 Flash Preview measured
ProofBench15.0%Not measuredOnly Gemini 3 Flash Preview measured
Neither model has a result on the other 5 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index71
Knowledge benchmarks for Gemini 3 Flash Preview and Grok 4.20
BenchmarkGemini 3 Flash PreviewGrok 4.20Leader
MMLU Pro88.6%86.3%Gemini 3 Flash Preview
LegalBench (Vals AI)86.9%77.7%Gemini 3 Flash Preview
CaseLaw (Vals AI)55.8%54.4%Gemini 3 Flash Preview
CorpFin (Vals AI)66.4%63.7%Gemini 3 Flash Preview
TaxEval (Vals AI)73.9%74.1%Grok 4.20
MortgageTax (Vals AI)68.7%45.4%Gemini 3 Flash Preview
MedQA (Vals AI)95.8%94.5%Gemini 3 Flash Preview
MedCode (Vals AI)55.9%32.2%Gemini 3 Flash Preview
MMLU Pro (Artificial Analysis run)89.0%Not measuredOnly Gemini 3 Flash Preview measured
SimpleQA Verified66.8%Not measuredOnly Gemini 3 Flash Preview measured
GeoBench88.0%Not measuredOnly Gemini 3 Flash Preview measured
Neither model has a result on the other 6 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index04
Web design benchmarks for Gemini 3 Flash Preview and Grok 4.20
BenchmarkGemini 3 Flash PreviewGrok 4.20Leader
Design Arena: websites11961229Grok 4.20
Design Arena: UI componentsNot measured1199Only Grok 4.20 measured
Design Arena: game dev11661192Grok 4.20
Design Arena: data vizNot measured1217Only Grok 4.20 measured
Design Arena: 3D11841193Grok 4.20
Design Arena: all code categories11891221Grok 4.20
Design Arena: SVGNot measured1164Only Grok 4.20 measured
Design Arena: ASCII artNot measured1174Only Grok 4.20 measured
Neither model has a result on the other 1 board here
GeneralLike-for-likePublic boards, shown as published, kept out of the index52
General benchmarks for Gemini 3 Flash Preview and Grok 4.20
BenchmarkGemini 3 Flash PreviewGrok 4.20Leader
SAGE (Vals AI)51.8%38.2%Gemini 3 Flash Preview
MedScribe (Vals AI)69.9%63.4%Gemini 3 Flash Preview
Vals Multimodal Index52.2%39.1%Gemini 3 Flash Preview
IFBench78.0%81.2%Grok 4.20
Long context reasoning (AA-LCR)78.0%69.0%Gemini 3 Flash Preview
DTBench89.1%90.1%Grok 4.20
LMCA43.1%38.7%Gemini 3 Flash Preview
CL-benchNot measured22.2%Only Grok 4.20 measured
CL-bench LifeNot measured11.9%Only Grok 4.20 measured
Neither model has a result on the other 37 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for Gemini 3 Flash Preview and Grok 4.20
BenchmarkGemini 3 Flash PreviewGrok 4.20Leader
Neither model has a result on 5 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

Gemini 3 Flash Preview$0.0020Fits in one request
Grok 4.20$0.0025Fits in one request

Gemini 3 Flash Preview costs less

Repository review

50K input + 3K output tokens

Gemini 3 Flash Preview$0.034Fits in one request
Grok 4.20$0.070Fits in one request

Gemini 3 Flash Preview costs less

Agent loop

200K input + 10K output tokens

Gemini 3 Flash Preview$0.130Fits in one request
Grok 4.20$0.275Fits in one request

Gemini 3 Flash Preview costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of Gemini 3 Flash Preview and Grok 4.20
SpecificationGoogle Gemini 3 Flash PreviewSpaceXAI Grok 4.20
MakerGooglexAI
WeightsNo public weights listedNo public weights listed
ReleasedDecember 17, 2025March 31, 2026
Context window1.05M2M
Input $/Mtok$0.50$1.25
Output $/Mtok$3.00$2.50
Coding index43.733.3
Independent measurements behind it22
Cost per solved task$0.37$0.72
SourceOpenRouter listingOpenRouter listing

Questions

Is Gemini 3 Flash Preview better than Grok 4.20 for coding?

Pick Gemini 3 Flash Preview for coding: it scores 43.7 on the Vibe Coding Index against 33.3 for Grok 4.20. Pick Grok 4.20 when output tokens cost 1.2x less, or when the context window is larger, 2M against 1.05M tokens.

Which is cheaper, Gemini 3 Flash Preview or Grok 4.20?

Gemini 3 Flash Preview costs $0.50 per million input tokens and $3.00 per million output tokens; Grok 4.20 costs $1.25 and $2.50. Per solved SWE-bench Verified task, Gemini 3 Flash Preview costs $0.37 and Grok 4.20 $0.72.

Which has the bigger context window, Gemini 3 Flash Preview or Grok 4.20?

Grok 4.20, with 2M tokens against 1.05M.

How many benchmarks is the Gemini 3 Flash Preview vs Grok 4.20 comparison based on?

46 benchmarks have a result for both models as of October 21, 2026. Gemini 3 Flash Preview's coding index rests on 2 independent benchmarks and Grok 4.20's on 2. Where only one model has a result, the page says so instead of naming a winner.

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<iframe src="https://llmbenchmark.ai/embed/compare/gemini-3-flash-preview-vs-grok-4-20" title="Gemini 3 Flash Preview vs Grok 4.20, LLMBenchmark.ai" width="100%" height="360" style="border:0;max-width:100%" loading="lazy"></iframe>
<p style="font:13px/1.4 sans-serif;margin:6px 0 0">Source: <a href="https://llmbenchmark.ai/compare/gemini-3-flash-preview-vs-grok-4-20">LLMBenchmark.ai, Gemini 3 Flash Preview vs Grok 4.20</a></p>