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Gemini 3.5 Flash vs GPT-5.3-Codex

Full profiles: Gemini 3.5 Flash (Google) and GPT-5.3-Codex (OpenAI): every benchmark, price and rank.

Updated · Data from 11 sources

As of 2 Nov 2026, Gemini 3.5 Flash and GPT-5.3-Codex are neck and neck on quality (62.5 vs 62.9 on the BenchLeader Index, inside the ±7.5 margin), and Gemini 3.5 Flash is 1.4× cheaper at $3.38 vs $4.81 per 1M tokens blended. Choose Gemini 3.5 Flash for multimodal (66 vs 61) and fast first answers (16.6 s vs 64.7 s), where it also streams ~2× faster; choose GPT-5.3-Codex for agents & tools (80 vs 63), long context (67 vs 61), and coding (61 vs 60).

Key facts (as of 2 Nov 2026)

  • Gemini 3.5 Flash scores 62.5 on the BenchLeader Index and GPT-5.3-Codex scores 62.9 (BenchLeader, 2 Nov 2026).
  • Gemini 3.5 Flash costs $3.38 per 1M tokens blended (list price, 2 Nov 2026).
  • GPT-5.3-Codex costs $4.81 per 1M tokens blended (list price, 2 Nov 2026).
  • Gemini 3.5 Flash streams ~2× faster than GPT-5.3-Codex (Artificial Analysis, 7-day median, 2 Nov 2026).
  • Of the 15 benchmarks both models have, Gemini 3.5 Flash leads 9 (BenchLeader, 2 Nov 2026).
Gemini 3.5 Flash benchmarks high Google GPT-5.3-Codex benchmarks xhigh OpenAIAdd a third model

Which to pick for…

The pick's numbers come first. Category scores on the BenchLeader scale (50 is the average model, 15 points one standard deviation). High confidence means a lead of half a standard deviation or more; under one point is called either.

Use casePickWhyConfidence
CodingGPT-5.3-Codex61 vs 60 category score; WeirdML 77.9% vs 62.6%Medium
Agents & tool useGPT-5.3-Codex80 vs 63 category score; Terminal-Bench Hard 53.0% vs 40.9%High
Long documentsGPT-5.3-Codex67 vs 61 category score; AA-LCR v1.1 83.3% vs 73.3%Medium
Images and other mediaGemini 3.5 Flash66 vs 61 category score; MMMU-Pro 84.3% vs 78.5%Medium
Following instructionsEither74 vs 74 category score; IFBench 76.3% vs 75.4%Either
Chat quality (human preference)–Only Gemini 3.5 Flash has an Arena rating (67 category score)Not comparable
Lowest costGemini 3.5 Flash$3.38 vs $4.81 per 1M blended; agentic coding session $0.126 vs $0.161–
Fastest first answerGemini 3.5 Flash16.6 s (Gemini 3.5 Flash (high)) vs 64.7 s (GPT-5.3-Codex (xhigh)) to the first answer token–
High volume on a budgetNeither flagshipA smaller model is usually the better fit: Cheapest good LLMs, Fastest LLMs–

Key differences

  • Gemini 3.5 Flash (high) and GPT-5.3-Codex (xhigh) are neck and neck on quality (62.5 vs 62.9, within the ±7.5 margin).
  • Gemini 3.5 Flash (high) is stronger in human preference, instruction following, knowledge, maths, multimodal, reasoning.
  • GPT-5.3-Codex (xhigh) is stronger in agents & tools, coding, long context.
  • Gemini 3.5 Flash (high) is 1.4× cheaper ($3.38 vs $4.81 per 1M blended).
  • Gemini 3.5 Flash (high) streams 1.7× faster (190 vs 114 tokens per second).

At a glance

SpecGemini 3.5 FlashGPT-5.3-Codex
DeveloperGoogleOpenAI
Released19 May 20265 Feb 2026
Context window (tokens)1,048,576400,000
Compared atGemini 3.5 Flash (high)GPT-5.3-Codex (xhigh)
Open weightsNoNo
Price in / out / cached input per 1M$1.50 / $9.00 / $0.150$1.75 / $14.00 / $0.175

Category by category

Category scores on the BenchLeader scale: 50 is the average evaluated model, 15 points is one standard deviation. A gap under one point is called level.

CategoryGemini 3.5 Flash (high)GPT-5.3-Codex (xhigh)Leader
Reasoning61.0–not comparable
Coding59.660.9GPT-5.3-Codex
Agents & tools63.480.0GPT-5.3-Codex
Maths58.1–not comparable
Knowledge63.4–not comparable
Instruction following74.373.5level
Human preference66.7–not comparable
Multimodal66.361.1Gemini 3.5 Flash
Long context61.466.6GPT-5.3-Codex

On one chart

Each domain on the index's own scale, where 50 is an average model. Click a domain to see the benchmarks behind it. Pick up to 5 models from the list.

2550 avg75CodingAgents & toolsInstructionfollowingLong contextMultimodalGemini 3.5 Flash, Coding: 59.6Gemini 3.5 Flash, Agents & tools: 63.4Gemini 3.5 Flash, Instruction following: 74.3Gemini 3.5 Flash, Long context: 61.4Gemini 3.5 Flash, Multimodal: 66.3GPT-5.3-Codex, Coding: 60.9GPT-5.3-Codex, Agents & tools: 80.0GPT-5.3-Codex, Instruction following: 73.5GPT-5.3-Codex, Long context: 66.6GPT-5.3-Codex, Multimodal: 61.1

Not drawn, measured for fewer than two of these models: Reasoning, Maths, Knowledge, Human preference.

ModelIndex

Where sources disagree

Across the 15 benchmarks both have, Gemini 3.5 Flash leads 9, GPT-5.3-Codex leads 6.

Overall indexGemini 3.5 Flash (high)GPT-5.3-Codex (xhigh)Leader
BenchLeader Index62.562.9neck and neck

Each publisher runs its own tasks, harnesses and effort settings, so their overall verdicts can differ; BenchLeader reconciles them on one scale. † measured at another effort setting of the same model (the publisher did not test the one compared here).

Price, speed and latency

List prices blended at three input tokens per output token. Per-task prices use the token counts on the methodology page. Cost, tokens and time per benchmark task are measured: Artificial Analysis’ averages over its whole Intelligence Index run.

MeasureGemini 3.5 Flash (high)GPT-5.3-Codex (xhigh)
Blended price per 1M tokens$3.38$4.81
Input / output per 1M$1.50 / $9.00$1.75 / $14.00
Cached input per 1M$0.150$0.175
Price per task: chat reply$0.0033$0.0049
Price per task: summarize a 30-page report$0.023$0.029
Price per task: code edit$0.022$0.032
Price per task: agentic coding session$0.126$0.161
Price per task: structured extraction$0.0048$0.0063
Agentic coding session, input mostly cached$0.065$0.090
Output speed190 tok/s114 tok/s
Time to first answer16.6 s64.7 s
Time to a complete answer19.3 s69.1 s

Each model is compared at its best-ranked reasoning-effort setting. Gemini 3.5 Flash (high) scores 62.5 and takes 17 s to its first answer token; Gemini 3.5 Flash (medium) scores 61.9 in 14 s, Gemini 3.5 Flash (minimal) scores 55.7 in 1 s. GPT-5.3-Codex (xhigh) scores 62.9 and takes 65 s to its first answer token. Higher effort means more thinking before the answer: better scores, longer waits and more tokens billed. How reasoning effort changes scores and cost.

Every benchmark

108 benchmarks, grouped by category; each name links to the board and its leaders. † measured at another effort setting of the same model, shown for reference and not counted as a win.

MetricPublisherGemini 3.5 Flash (high)GPT-5.3-Codex (xhigh)
BenchLeader IndexBenchLeader62.562.9
Agents & tools scoreBenchLeader63.480.0
Coding scoreBenchLeader59.660.9
Human preference scoreBenchLeader66.7–
Instruction following scoreBenchLeader74.373.5
Knowledge scoreBenchLeader63.4–
Long context scoreBenchLeader61.466.6
Maths scoreBenchLeader58.1–
Multimodal scoreBenchLeader66.361.1
Reasoning scoreBenchLeader61.0–
Blended price $/MBenchLeader$3.38$4.81
Output speedBenchLeader190 tok/s114 tok/s
Time to first answerBenchLeader16.6 s64.7 s
Context windowBenchLeader1,048,576 tokens400,000 tokens
Reasoning
GPQA DiamondEpoch AI Benchmarking Hub92.8%–
SimpleBenchSimpleBench76.7%†–
Arena Hard PromptsArena (LMArena)1495–
LiveBench 1.0 ReasoningLiveBench82.0%–
GPQA Diamond (AA)Artificial Analysis92.2%91.5%
Humanity's Last Exam (AA)Artificial Analysis42.7%42.5%
GPQA Diamond (Vals)Vals AI92.7%–
EnigmaEvalScale AI SEAL25.4%–
ARC-AGI-1ARC Prize92.5%–
ARC-AGI-2ARC Prize72.1%–
CritPtArtificial Analysis13.1%16.9%
Chess PuzzlesEpoch AI Benchmarking Hub45.0%–
Mystery Game PuzzlesEpoch AI Benchmarking Hub32.0%–
LMCAEpoch AI Benchmarking Hub47.1%–
DTBenchEpoch AI Benchmarking Hub94.7%–
ForecastBenchForecastBench64.4%†–
Coding
SWE-bench Verified (Epoch)Epoch AI Benchmarking Hub79.3%74.8%†
SciCodeSciCode53.9%–
WeirdMLWeirdML62.6%77.9%
Arena CodingArena (LMArena)1508–
Arena WebDevArena (LMArena)14991407†
LiveBench 1.0 CodingLiveBench78.2%–
LiveCodeBenchVals AI87.6%87.3%
IOIVals AI–53.8%
SWE-bench (Vals)Vals AI78.8%78.0%
Show all 108 benchmarks
MetricPublisherGemini 3.5 Flash (high)GPT-5.3-Codex (xhigh)
Coding
Code MigrationVals AI26.8%–
ProgramBenchVals AI0.0%–
Vibe Code Bench v1.1Vals AI48.7%61.8%
Surface Evolver BenchEpoch AI Benchmarking Hub58.1%†–
DeepSWE v1.1Epoch AI Benchmarking Hub36.1%–
ALE-BenchEpoch AI Benchmarking Hub911.01655.2
Terminal-Bench 4.0 (AA)Artificial Analysis6.6%–
Terminal-Bench 2.1 (AA)Artificial Analysis78.7%–
GameBench 2 OverallDuelLab GameBench 251.1†–
GameBench 2 by reasoning settingDuelLab GameBench 264.1–
Agents & tools
Terminal-BenchTerminal-Bench–78.4%†
APEX-AgentsMercor27.5%†–
LiveBench Agentic CodingLiveBench49.0%–
Terminal-Bench HardArtificial Analysis40.9%53.0%
τ²-Bench Telecom (AA)Artificial Analysis95.3%86.0%
Terminal-Bench 2.1 (Vals)Vals AI74.2%–
MCP AtlasScale AI SEAL83.6%–
HiL-BenchScale AI SEAL27.7%†4.3%†
τ³-Banking (AA)Artificial Analysis32.2%–
ITBench SRE (AA)Artificial Analysis40.4%–
Analyst Agent (AA)Artificial Analysis45.0%–
APEX-Agents (AA)Artificial Analysis47.0%–
Finance Agent v2Vals AI57.9%–
Harvey's Legal Agent Benchmark v1Vals AI2.5%–
Legal Research BenchVals AI30.8%–
SkillsBenchVals AI52.7%–
Tax Agent BenchVals AI21.6%–
Terminal-Bench 2.0 (Vals)Vals AI67.4%64.0%†
Terminal-Bench 4.0 (Vals)Vals AI6.1%–
Terminal-Bench ScienceVals AI5.7%–
Web Search IndexVals AI37.0%–
METR Time HorizonsMETR–74.5%†
GBAEvalEpoch AI Benchmarking Hub6.7%†–
Vending-Bench 2Andon Labs5396.4†5940.1†
AutomationBenchArtificial Analysis42.1%–
GDP.pdf (AA)Artificial Analysis19.8%–
EnterpriseOps-GymArtificial Analysis50.1%–
AA-Briefcase v1.1Artificial Analysis875868
FACTS SearchGoogle64.3%†–
Maths
FrontierMath Tiers 1–3Epoch AI Benchmarking Hub62.8%–
FrontierMath Tier 4Epoch AI Benchmarking Hub26.8%–
OTIS Mock AIMEEpoch AI Benchmarking Hub95.6%–
ProofBenchVals AI31.0%–
LiveBench MathematicsLiveBench88.2%–
AIME 2026MathArena95.0%†–
HMMT February 2026MathArena95.5%†–
MathArena ApexMathArena32.3%†–
Arena MathsArena (LMArena)1497–
Knowledge
SimpleQA VerifiedEpoch AI Benchmarking Hub66.2%–
LiveBench 1.0 Data AnalysisLiveBench64.9%–
MMLU-ProVals AI89.5%–
LegalBenchVals AI83.6%–
CorpFinVals AI64.7%–
TaxEvalVals AI74.4%–
Excel Modeling BenchmarkVals AI63.5%–
MedCodeVals AI55.8%–
MedScribeVals AI76.6%–
Public Benefits Bench v1.1Vals AI59.5%–
DrugDiscoveryBenchScale AI SEAL50.0%–
EBR-benchEpoch AI Benchmarking Hub4.8%–
GDP.pdfEpoch AI Benchmarking Hub14.0%†–
Instruction following
LiveBench LanguageLiveBench84.6%–
LiveBench Instruction FollowingLiveBench75.6%–
IFBenchArtificial Analysis76.3%75.4%
Arena Instruction FollowingArena (LMArena)1465–
Human preference
Arena TextArena (LMArena)1478–
EQ-Bench 4EQ-Bench1077†–
Arena Creative WritingArena (LMArena)1465–
Arena Multi-turnArena (LMArena)1480–
Arena Longer QueriesArena (LMArena)1482–
Multimodal
Arena VisionArena (LMArena)1308–
MMMU-ProArtificial Analysis84.3%78.5%
MMMU-Pro (Vals)Vals AI88.3%–
MortgageTaxVals AI68.1%–
Blueprint-Bench 2Epoch AI Benchmarking Hub33.6%†–
Long context
AA-LCR v1.1Artificial Analysis73.3%83.3%
Arena DocumentArena (LMArena)1453–
MLCRArtificial Analysis10.0%–
Composite
Epoch Capabilities IndexEpoch AI Benchmarking Hub155.0†–
LiveBench 1.0LiveBench74.6%–
AA Intelligence Index v4.3.2Artificial Analysis32.632.5
AA Progress Index v1Artificial Analysis305.1301.3
Vals Multimodal IndexVals AI62.9%–

Data as of 2026-11-02. Best configuration of each model; every score links to its source on the model pages.

DuelLab GameBench 2, release gb2-20261026-cb69502a12d9 (https://benchmarks.duellab.org/releases/gb2-20261026-cb69502a12d9/), CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Scores mapped to BenchLeader model names; not endorsed by DuelLab.

What changed

  • GPT-5.3-Codex (xhigh): 1 new result (AA-Briefcase v1.1).
  • Gemini 3.5 Flash (high): BenchLeader Index 63.2 → 62.6.
  • Gemini 3.5 Flash (high): 1 new result (AA Progress Index v1).
  • GPT-5.3-Codex (xhigh): 1 new result (AA Progress Index v1).
  • Gemini 3.5 Flash (high): cost per task moved from $3.69/M to $2.98/M (19% down).
  • Gemini 3.5 Flash (high): 1 new result (Harvey's Legal Agent Benchmark v1).
  • Gemini 3.5 Flash (high): 1 score revision.
  • Gemini 3.5 Flash (high): 3 new results (GDPval-AA v2.1, normalised score, AA-Omniscience v1.1: accuracy, AA-Omniscience v1.1: non-hallucination).
  • Gemini 3.5 Flash (high): 1 score revision.
  • Gemini 3.5 Flash (high): 2 score revisions.

Rankings: Best LLM overall · Best LLM for agents · Best cheap LLMs

Gemini 3.5 Flash vs GPT-5.3-Codex: questions

Is Gemini 3.5 Flash better than GPT-5.3-Codex?
Gemini 3.5 Flash (high) and GPT-5.3-Codex (xhigh) are neck and neck on quality (62.5 vs 62.9, within the ±7.5 margin). The BenchLeader Index combines every independent quality benchmark; the two are within the margin of error as of 2 Nov 2026, so check the category scores for your use.
Gemini 3.5 Flash vs GPT-5.3-Codex: which is cheaper, and will that change?
Gemini 3.5 Flash is cheaper today: $3.38 against $4.81 per million tokens, blended at three input tokens per output token. No price change has been announced for either.
Is Gemini 3.5 Flash or GPT-5.3-Codex better for coding?
GPT-5.3-Codex scores higher in coding (61 vs 60 on the category index, where 50 is average). On LiveCodeBench, the top shared coding benchmark, it is 87.6% for Gemini 3.5 Flash against 87.3% for GPT-5.3-Codex.
Which is faster, Gemini 3.5 Flash or GPT-5.3-Codex?
Gemini 3.5 Flash streams ~2× faster (190 vs 114 output tokens per second, Artificial Analysis 7-day median).
Is Gemini 3.5 Flash or GPT-5.3-Codex better for agents and tool use?
GPT-5.3-Codex scores higher in agentic tasks (80 vs 63 on the category index, where 50 is average). On Terminal-Bench Hard, the top shared agents & tools benchmark, it is 40.9% for Gemini 3.5 Flash against 53.0% for GPT-5.3-Codex.
More questions (4)
Which is better for long documents?
GPT-5.3-Codex scores higher on long-context benchmarks (67 vs 61). Gemini 3.5 Flash accepts more context: 1,048,576 against 400,000 tokens for GPT-5.3-Codex.
Which has lower latency?
Gemini 3.5 Flash answers first: 16.6 s against 64.7 s to the first answer token, as Artificial Analysis measures it. Reasoning effort drives most of this: a higher setting thinks longer before it answers.
Do independent benchmarks agree on Gemini 3.5 Flash vs GPT-5.3-Codex?
Across the 15 benchmarks both have, Gemini 3.5 Flash leads 9, GPT-5.3-Codex leads 6.
When was Gemini 3.5 Flash released?
Gemini 3.5 Flash was released on 19 May 2026.