Gemini 3 Flash Preview vs GPT-5.3-Codex
Updated October 21, 2026. 23 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Pick Gemini 3 Flash Preview for coding: it scores 75.8 on the Vibe Coding Index against 29.5 for GPT-5.3-Codex.
Pick GPT-5.3-Codex when what matters is LiveCodeBench (Vals AI) or SWE-bench Verified (Vals AI), where it leads.
- Shared results
- 23
- Gemini 3 Flash Preview only
- 46
- GPT-5.3-Codex only
- 11
- Like-for-like categories
- 6 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.
Coding
Vibe Coding Index, four public coding benchmarks
Gemini 3 Flash Preview
Gemini 3 Flash Preview scores 75.8 against 29.5.
One benchmark behind each score
Intelligence
AA Intelligence Index
GPT-5.3-Codex
GPT-5.3-Codex leads, 32.5 against 26.3.
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 1163.
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-5.3-Codex $0.0088 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-5.3-Codex $0.59.
Published attempt cost and pass rate
At a glance
- Coding index
- Gemini 3 Flash Preview 75.8 from 1 benchmark, GPT-5.3-Codex 29.5 from 1 benchmark.
- Widest category
- Coding, 14.6 points apart on average over 7 shared benchmarks.
- Widest single gap
- Vibe Code Bench (Vals AI): Gemini 3 Flash Preview 20.2% against GPT-5.3-Codex 61.8%, 41.6 points apart on a 0 to 100 scale.
- Output price
- Gemini 3 Flash Preview $3.00 against GPT-5.3-Codex $14.00 per million output tokens, 4.7x apart.
- Context window
- Gemini 3 Flash Preview takes 1.05M tokens, GPT-5.3-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.
| Category | Gemini 3 Flash Preview | Bars | GPT-5.3-Codex | Ties |
|---|---|---|---|---|
| Coding | 0 | 7 | ||
| Intelligence | 0 | 1 | ||
| Agentic work | 4 | 3 | ||
| Reasoning | 0 | 2 | ||
| Web design | 4 | 0 | ||
| General | 1 | 1 | ||
| All shared boards | 9 | 14 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index07
| Benchmark | Gemini 3 Flash Preview | GPT-5.3-Codex | Leader |
|---|---|---|---|
| SWE-bench Verified | 75.8% | Not measured | Only Gemini 3 Flash Preview measured |
| LMArena WebDev | Not measured | 1407 | Only GPT-5.3-Codex measured |
| LiveCodeBench (Vals AI) | 85.6% | 87.3% | GPT-5.3-Codex |
| SWE-bench Verified (Vals AI) | 75.0% | 78.0% | GPT-5.3-Codex |
| Vibe Code Bench (Vals AI) | 20.2% | 61.8% | GPT-5.3-Codex |
| 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 |
| IOI (Vals AI) | Not measured | 53.8% | Only GPT-5.3-Codex measured |
| Terminal-Bench 2.1 (Vals AI) | 53.9% | Not measured | Only Gemini 3 Flash Preview measured |
| LiveCodeBench (Artificial Analysis run) | 90.8% | Not measured | Only Gemini 3 Flash Preview measured |
| Terminal-Bench Hard (Artificial Analysis run) | 38.6% | 53.0% | GPT-5.3-Codex |
| Terminal-Bench | 64.3% | 78.4% | GPT-5.3-Codex |
| GSO-Bench | 9.8% | Not measured | Only Gemini 3 Flash Preview measured |
| WeirdML | 61.6% | 79.3% | GPT-5.3-Codex |
| ALE-Bench | 1367.2 | 1655.2 | GPT-5.3-Codex |
| LMArena WebDev: React | Not measured | 1395 | Only GPT-5.3-Codex measured |
| LMArena WebDev: HTML | Not measured | 1422 | Only GPT-5.3-Codex measured |
| LMArena WebDev: from an image | Not measured | 1443 | Only GPT-5.3-Codex measured |
| Neither model has a result on the other 20 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Gemini 3 Flash Preview | GPT-5.3-Codex | Leader |
|---|---|---|---|
| AA Intelligence Index | 26.3 | 32.5 | GPT-5.3-Codex |
| Epoch Capabilities Index | Not measured | 157.1 | Only GPT-5.3-Codex measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index43
| Benchmark | Gemini 3 Flash Preview | GPT-5.3-Codex | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1111 | 1033 | Gemini 3 Flash Preview |
| Design Arena: agents building full-stack apps | 1063 | 983 | Gemini 3 Flash Preview |
| Design Arena: agents building mobile apps | 1090 | 1054 | Gemini 3 Flash Preview |
| Design Arena: agents building Android apps | 1056 | 1084 | GPT-5.3-Codex |
| Design Arena: agents building Godot games | 1161 | 1124 | Gemini 3 Flash Preview |
| 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% | 86.0% | GPT-5.3-Codex |
| METR time horizons | Not measured | 74.5% | Only GPT-5.3-Codex measured |
| 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 | $5,940 | GPT-5.3-Codex |
| Neither model has a result on the other 24 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Gemini 3 Flash Preview | GPT-5.3-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% | 91.5% | GPT-5.3-Codex |
| Humanity's Last Exam (Artificial Analysis run) | 36.6% | 42.5% | GPT-5.3-Codex |
| 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 10 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | Gemini 3 Flash Preview | GPT-5.3-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 | Not measured | Only Gemini 3 Flash Preview measured |
| AIME 2025 (Artificial Analysis run) | 97.0% | Not measured | Only Gemini 3 Flash Preview measured |
| 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 5 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index11 boards, none shared
| Benchmark | Gemini 3 Flash Preview | GPT-5.3-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% | Not measured | Only Gemini 3 Flash Preview measured |
| SimpleQA Verified | 66.8% | Not measured | Only Gemini 3 Flash Preview measured |
| GeoBench | 88.0% | Not measured | Only 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 index40
| Benchmark | Gemini 3 Flash Preview | GPT-5.3-Codex | Leader |
|---|---|---|---|
| Design Arena: websites | 1196 | 1163 | Gemini 3 Flash Preview |
| Design Arena: UI components | Not measured | 1137 | Only GPT-5.3-Codex measured |
| Design Arena: game dev | 1166 | 1162 | Gemini 3 Flash Preview |
| Design Arena: data viz | Not measured | 1164 | Only GPT-5.3-Codex measured |
| Design Arena: 3D | 1184 | 1008 | Gemini 3 Flash Preview |
| Design Arena: all code categories | 1189 | 1145 | Gemini 3 Flash Preview |
| Design Arena: SVG | Not measured | 1129 | Only GPT-5.3-Codex measured |
| Design Arena: ASCII art | Not measured | 1151 | Only GPT-5.3-Codex measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index11
| Benchmark | Gemini 3 Flash Preview | GPT-5.3-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% | 75.4% | Gemini 3 Flash Preview |
| Long context reasoning (AA-LCR) | 78.0% | 83.3% | GPT-5.3-Codex |
| 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 39 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Gemini 3 Flash Preview | GPT-5.3-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 costs less
Repository review
50K input + 3K output tokens
Gemini 3 Flash Preview costs less
Agent loop
200K input + 10K output tokens
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.
| Specification | Google Gemini 3 Flash Preview | OpenAI GPT-5.3-Codex |
|---|---|---|
| Maker | OpenAI | |
| Weights | No public weights listed | No public weights listed |
| Released | December 17, 2025 | February 24, 2026 |
| Context window | 1.05M | 400K |
| Input $/Mtok | $0.50 | $1.75 |
| Output $/Mtok | $3.00 | $14.00 |
| Coding index | 75.8 | 29.5 |
| Independent measurements behind it | 1 | 1 |
| Cost per solved task | $0.37 | $0.59 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Gemini 3 Flash Preview better than GPT-5.3-Codex for coding?
Pick Gemini 3 Flash Preview for coding: it scores 75.8 on the Vibe Coding Index against 29.5 for GPT-5.3-Codex. Pick GPT-5.3-Codex when what matters is LiveCodeBench (Vals AI) or SWE-bench Verified (Vals AI), where it leads.
Which is cheaper, Gemini 3 Flash Preview or GPT-5.3-Codex?
Gemini 3 Flash Preview costs $0.50 per million input tokens and $3.00 per million output tokens; GPT-5.3-Codex costs $1.75 and $14.00. Per solved SWE-bench Verified task, Gemini 3 Flash Preview costs $0.37 and GPT-5.3-Codex $0.59.
Which has the bigger context window, Gemini 3 Flash Preview or GPT-5.3-Codex?
Gemini 3 Flash Preview, with 1.05M tokens against 400K.
How many benchmarks is the Gemini 3 Flash Preview vs GPT-5.3-Codex comparison based on?
23 benchmarks have a result for both models as of October 21, 2026. Gemini 3 Flash Preview's coding index rests on 1 independent benchmark and GPT-5.3-Codex's on 1. Where only one model has a result, the page says so instead of naming a winner.