Gemini 3 Flash Preview vs GPT-5.1-Codex

Gemini 3 Flash Preview leads GPT-5.1-Codex on coding, 43.7 to 15.3 on the Vibe Coding Index, and Gemini 3 Flash Preview costs 3.3x less per output token ($3.00 vs $10.00 per million). Updated October 22, 2026; 22 benchmarks have a result for both.

Replace Gemini 3 Flash Preview Replace GPT-5.1-Codex

Gemini 3 Flash PreviewGoogle

Coding: 43.7
Overall: 55.0
Output $/M: $3.00

GPT-5.1-CodexOpenAI

Coding: 15.3
Overall: No data
Output $/M: $10.00

vs boards won of 22 shared

Gemini 3 Flash Preview or GPT-5.1-Codex: which to pick

Pick Gemini 3 Flash Preview for coding: it scores 43.7 on the Vibe Coding Index against 15.3 for GPT-5.1-Codex.

Pick GPT-5.1-Codex for work measured by Design Arena: agents building full-stack apps or Design Arena: agents building mobile apps, where it leads.

Model AGemini 3 Flash PreviewGoogle43.7/1002 independent benchmarks$0.37 per solved task Model BGPT-5.1-CodexOpenAI15.3/1002 independent benchmarks$0.892 per solved task

22504

Shared results: 22
Gemini 3 Flash Preview only: 50
GPT-5.1-Codex only: 4
Like-for-like categories: 8 of 9

Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.

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.

Coding
Vibe Coding Index, six public coding benchmarks
Gemini 3 Flash Preview
Gemini 3 Flash Preview scores 43.7 against 15.3.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
Gemini 3 Flash Preview
Gemini 3 Flash Preview leads, 26.3 against 23.7.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only Gemini 3 Flash Preview has a GPQA Diamond result, 87.9%.
Directional only
Math
AIME
No call
Only Gemini 3 Flash Preview has a AIME result, 95.6%.
Directional only
Knowledge
MMLU Pro
No call
Only Gemini 3 Flash Preview has a MMLU Pro result, 88.6%.
Directional only
Web design
Design Arena: websites
Gemini 3 Flash Preview
Gemini 3 Flash Preview leads, 1196 against 1161.
Same board, both measured
Long documents
Listed context window
Gemini 3 Flash Preview
Gemini 3 Flash Preview takes 1.05M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Gemini 3 Flash Preview
Gemini 3 Flash Preview $0.0020, GPT-5.1-Codex $0.0063 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
Gemini 3 Flash Preview
Gemini 3 Flash Preview $0.37, GPT-5.1-Codex $0.892.
Published attempt cost and pass rate

At a glance

Coding index: Gemini 3 Flash Preview 43.7 from 2 benchmarks, GPT-5.1-Codex 15.3 from 2 benchmarks.
Widest category: General, 8.3 points apart on average over 2 shared benchmarks.
Widest single gap: Design Arena: agents building mobile apps: Gemini 3 Flash Preview 1090 against GPT-5.1-Codex 1191, 12.6 points apart on a 0 to 100 scale.
Output price: Gemini 3 Flash Preview $3.00 against GPT-5.1-Codex $10.00 per million output tokens, 3.3x apart.
Context window: Gemini 3 Flash Preview takes 1.05M tokens, GPT-5.1-Codex 400K.

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
Category	Gemini 3 Flash Preview	GPT-5.1-Codex
Coding	7	0
Intelligence	1	0
Agentic work	1	3
Reasoning	2	0
Math	2	0
Knowledge	1	0
Web design	3	0
General	2	0
All shared boards	19	3

CodingLike-for-likeSix of these boards feed the Vibe Coding Index70

Coding benchmarks for Gemini 3 Flash Preview and GPT-5.1-Codex
Benchmark	Gemini 3 Flash Preview	GPT-5.1-Codex	Leader
SWE-bench Verified	75.8%	66.0%	Gemini 3 Flash Preview
LMArena WebDev	Not measured	1337	Only GPT-5.1-Codex measured
LiveCodeBench (Vals AI)	85.6%	85.5%	Gemini 3 Flash Preview
SWE-bench Verified (Vals AI)	75.0%	Not measured	Only Gemini 3 Flash Preview measured
Vibe Code Bench (Vals AI)	20.2%	13.1%	Gemini 3 Flash Preview
Code migration (Vals AI)	6.4%	Not measured	Only Gemini 3 Flash Preview measured
ProgramBench (Vals AI)	0.0%	Not measured	Only Gemini 3 Flash Preview measured
Terminal-Bench 2.1 (Vals AI)	53.9%	Not measured	Only Gemini 3 Flash Preview measured
LiveCodeBench (Artificial Analysis run)	90.8%	84.9%	Gemini 3 Flash Preview
Terminal-Bench Hard (Artificial Analysis run)	38.6%	34.8%	Gemini 3 Flash Preview
Terminal-Bench	64.3%	57.8%	Gemini 3 Flash Preview
GSO-Bench	9.8%	Not measured	Only Gemini 3 Flash Preview measured
WeirdML	61.6%	Not measured	Only Gemini 3 Flash Preview measured
ALE-Bench	1367.2	1244.9	Gemini 3 Flash Preview
LMArena WebDev: HTML	Not measured	1346	Only GPT-5.1-Codex measured
SciCode	12.7%	Not measured	Only Gemini 3 Flash Preview measured
Neither model has a result on the other 27 boards here

IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10

Intelligence benchmarks for Gemini 3 Flash Preview and GPT-5.1-Codex
Benchmark	Gemini 3 Flash Preview	GPT-5.1-Codex	Leader
AA Intelligence Index	26.3	23.7	Gemini 3 Flash Preview
Neither model has a result on the other 1 board here

Agentic workLike-for-likePublic boards, shown as published, kept out of the index13

Agentic work benchmarks for Gemini 3 Flash Preview and GPT-5.1-Codex
Benchmark	Gemini 3 Flash Preview	GPT-5.1-Codex	Leader
Design Arena: agents building web apps	1111	1018	Gemini 3 Flash Preview
Design Arena: agents building full-stack apps	1063	1086	GPT-5.1-Codex
Design Arena: agents building mobile apps	1090	1191	GPT-5.1-Codex
Design Arena: agents building Android apps	1051	Not measured	Only Gemini 3 Flash Preview measured
Design Arena: agents building Godot games	1161	Not measured	Only Gemini 3 Flash Preview measured
Design Arena: PowerPoint slides	1036	Not measured	Only Gemini 3 Flash Preview measured
Finance Agent (Vals AI)	42.5%	Not measured	Only Gemini 3 Flash Preview measured
Tax Agent Bench (Vals AI)	11.8%	Not measured	Only Gemini 3 Flash Preview measured
Legal Research Bench (Vals AI)	18.3%	Not measured	Only Gemini 3 Flash Preview measured
Excel Modeling Benchmark (Vals AI)	26.0%	Not measured	Only Gemini 3 Flash Preview measured
τ²-Bench Telecom	80.4%	83.0%	GPT-5.1-Codex
BALROG	48.1%	Not measured	Only Gemini 3 Flash Preview measured
DeepResearch Bench	49.8%	Not measured	Only Gemini 3 Flash Preview measured
Vending-Bench 2	$3,635	Not measured	Only Gemini 3 Flash Preview measured
MCP Atlas	62.0%	Not measured	Only Gemini 3 Flash Preview measured
Neither model has a result on the other 27 boards here

ReasoningLike-for-likePublic boards, shown as published, kept out of the index20

Reasoning benchmarks for Gemini 3 Flash Preview and GPT-5.1-Codex
Benchmark	Gemini 3 Flash Preview	GPT-5.1-Codex	Leader
GPQA Diamond	87.9%	Not measured	Only Gemini 3 Flash Preview measured
MMMU Pro (Vals AI)	87.6%	Not measured	Only Gemini 3 Flash Preview measured
GPQA Diamond (Artificial Analysis run)	89.8%	86.0%	Gemini 3 Flash Preview
Humanity's Last Exam (Artificial Analysis run)	36.6%	25.7%	Gemini 3 Flash Preview
GPQA Diamond (Epoch AI run)	89.4%	Not measured	Only Gemini 3 Flash Preview measured
ARC-AGI	84.7%	Not measured	Only Gemini 3 Flash Preview measured
ARC-AGI-2	33.6%	Not measured	Only Gemini 3 Flash Preview measured
SimpleBench	61.1%	Not measured	Only Gemini 3 Flash Preview measured
Chess puzzles	39.0%	Not measured	Only Gemini 3 Flash Preview measured
Mystery game puzzles	26.0%	Not measured	Only Gemini 3 Flash Preview measured
VPCT	72.6%	Not measured	Only Gemini 3 Flash Preview measured
Neither model has a result on the other 12 boards here

MathLike-for-likePublic boards, shown as published, kept out of the index20

Math benchmarks for Gemini 3 Flash Preview and GPT-5.1-Codex
Benchmark	Gemini 3 Flash Preview	GPT-5.1-Codex	Leader
AIME	95.6%	Not measured	Only Gemini 3 Flash Preview measured
MGSM (Vals AI)	93.3%	Not measured	Only Gemini 3 Flash Preview measured
AA Math Index	97.0	95.7	Gemini 3 Flash Preview
AIME 2025 (Artificial Analysis run)	97.0%	95.7%	Gemini 3 Flash Preview
OTIS Mock AIME	95.6%	Not measured	Only Gemini 3 Flash Preview measured
FrontierMath, tiers 1 to 3	51.2%	Not measured	Only Gemini 3 Flash Preview measured
FrontierMath, tier 4	17.1%	Not measured	Only Gemini 3 Flash Preview measured
ProofBench	15.0%	Not measured	Only Gemini 3 Flash Preview measured
Neither model has a result on the other 6 boards here

KnowledgeLike-for-likePublic boards, shown as published, kept out of the index10

Knowledge benchmarks for Gemini 3 Flash Preview and GPT-5.1-Codex
Benchmark	Gemini 3 Flash Preview	GPT-5.1-Codex	Leader
MMLU Pro	88.6%	Not measured	Only Gemini 3 Flash Preview measured
LegalBench (Vals AI)	86.9%	Not measured	Only Gemini 3 Flash Preview measured
CaseLaw (Vals AI)	55.8%	Not measured	Only Gemini 3 Flash Preview measured
CorpFin (Vals AI)	66.4%	Not measured	Only Gemini 3 Flash Preview measured
TaxEval (Vals AI)	73.9%	Not measured	Only Gemini 3 Flash Preview measured
MortgageTax (Vals AI)	68.7%	Not measured	Only Gemini 3 Flash Preview measured
MedQA (Vals AI)	95.8%	Not measured	Only Gemini 3 Flash Preview measured
MedCode (Vals AI)	55.9%	Not measured	Only Gemini 3 Flash Preview measured
MMLU Pro (Artificial Analysis run)	89.0%	86.0%	Gemini 3 Flash Preview
SimpleQA Verified	66.8%	Not measured	Only Gemini 3 Flash Preview measured
GeoBench	88.0%	Not measured	Only Gemini 3 Flash Preview measured
FACTS Benchmark Suite	63.4%	Not measured	Only Gemini 3 Flash Preview measured
Neither model has a result on the other 8 boards here

Web designLike-for-likePublic boards, shown as published, kept out of the index30

Web design benchmarks for Gemini 3 Flash Preview and GPT-5.1-Codex
Benchmark	Gemini 3 Flash Preview	GPT-5.1-Codex	Leader
Design Arena: websites	1196	1161	Gemini 3 Flash Preview
Design Arena: UI components	Not measured	1235	Only GPT-5.1-Codex measured
Design Arena: game dev	1165	1137	Gemini 3 Flash Preview
Design Arena: data viz	Not measured	1213	Only GPT-5.1-Codex measured
Design Arena: 3D	1183	Not measured	Only Gemini 3 Flash Preview measured
Design Arena: all code categories	1189	1152	Gemini 3 Flash Preview
Neither model has a result on the other 3 boards here

GeneralLike-for-likePublic boards, shown as published, kept out of the index20

General benchmarks for Gemini 3 Flash Preview and GPT-5.1-Codex
Benchmark	Gemini 3 Flash Preview	GPT-5.1-Codex	Leader
SAGE (Vals AI)	51.8%	Not measured	Only Gemini 3 Flash Preview measured
MedScribe (Vals AI)	69.9%	Not measured	Only Gemini 3 Flash Preview measured
Vals Multimodal Index	52.2%	Not measured	Only Gemini 3 Flash Preview measured
IFBench	78.0%	70.0%	Gemini 3 Flash Preview
Long context reasoning (AA-LCR)	78.0%	69.3%	Gemini 3 Flash Preview
DTBench	89.1%	Not measured	Only Gemini 3 Flash Preview measured
LMCA	43.1%	Not measured	Only Gemini 3 Flash Preview measured
Neither model has a result on the other 41 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 GPT-5.1-Codex
Benchmark	Gemini 3 Flash Preview	GPT-5.1-Codex	Leader
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

GPT-5.1-Codex$0.0063Fits 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

GPT-5.1-Codex$0.092Fits 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

GPT-5.1-Codex$0.350Fits 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 GPT-5.1-Codex
Specification	Google Gemini 3 Flash Preview	OpenAI GPT-5.1-Codex
Maker	Google	OpenAI
Weights	No public weights listed	No public weights listed
Released	December 17, 2025	November 13, 2025
Context window	1.05M	400K
Input $/Mtok	$0.50	$1.25
Output $/Mtok	$3.00	$10.00
Coding index	43.7	15.3
Independent measurements behind it	2	2
Cost per solved task	$0.37	$0.892
Source	OpenRouter listing	OpenRouter listing

Questions

Is Gemini 3 Flash Preview better than GPT-5.1-Codex for coding?

Pick Gemini 3 Flash Preview for coding: it scores 43.7 on the Vibe Coding Index against 15.3 for GPT-5.1-Codex. Pick GPT-5.1-Codex for work measured by Design Arena: agents building full-stack apps or Design Arena: agents building mobile apps, where it leads.

Which is cheaper, Gemini 3 Flash Preview or GPT-5.1-Codex?

Gemini 3 Flash Preview costs $0.50 per million input tokens and $3.00 per million output tokens; GPT-5.1-Codex costs $1.25 and $10.00. Per solved SWE-bench Verified task, Gemini 3 Flash Preview costs $0.37 and GPT-5.1-Codex $0.892.

Which has the bigger context window, Gemini 3 Flash Preview or GPT-5.1-Codex?

Gemini 3 Flash Preview, with 1.05M tokens against 400K.

How many benchmarks is the Gemini 3 Flash Preview vs GPT-5.1-Codex comparison based on?

22 benchmarks have a result for both models as of October 22, 2026. Gemini 3 Flash Preview's coding index rests on 2 independent benchmarks and GPT-5.1-Codex's on 2. Where only one model has a result, the page says so instead of naming a winner.

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Gemini 3 Flash Preview or GPT-5.1-Codex: which to pick

Which one for your work

Coding

Intelligence

Reasoning

Math

Knowledge

Web design

Long documents

Everyday cost

Cost per solved task

At a glance

Benchmark by benchmark

What each workload costs

Chat turn

Repository review

Agent loop

Specification differences

Questions

Compare next