Model comparison
Gemini 3 Flash Preview vs GPT-5.1-Codex
Gemini 3 Flash Preview is the stronger model overall, scoring 52.3 to 38.6 on the Noometry Index.
Last verified . 5 shared benchmarks.
GoogleSummary
- They share 5 benchmarks with published results for both. Gemini 3 Flash Preview scores higher in 3 categories and GPT-5.1-Codex in 0 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in math, where Gemini 3 Flash Preview leads 51.7 to 30.3.
- The biggest single-benchmark swing is SWE-bench Verified (bash only): 75.8% for Gemini 3 Flash Preview and 66% for GPT-5.1-Codex.
- Gemini 3 Flash Preview is cheaper at $0.50 / $3 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- Gemini 3 Flash Preview accepts more context: 1.05M tokens versus 400K.
Side by side
| Gemini 3 Flash Preview | GPT-5.1-Codex | |
|---|---|---|
| Provider | OpenAI | |
| Noometry Index | 52.3 | 38.6 |
| Released | 2025-12-17 | 2025-11-12 |
| Weights | Proprietary | Proprietary |
| Context window | 1.05M | 400K |
| Max output | 66K | 128K |
| Input $ / M tokens | $0.50 | $1.25 |
| Output $ / M tokens | $3 | $10 |
| Results tracked | 59 | 6 |
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Category by category
Coding Gemini 3 Flash Preview leads
Gemini 3 Flash Preview: 50.9 (#42), GPT-5.1-Codex: 41.9 (#116)
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| SWE-bench Verified (bash only) | 75.8% | 66% |
| LMArena WebDev | 1439 | 1337 |
| ALE-Bench | 1,367 | 1,245 |
| SWE-bench Verified | 75.4% | — |
| SWE-bench Multilingual | 72.7% | — |
| GSO | 9.8% | — |
| WeirdML | 61.6% | — |
| LMArena Coding | 1460 | — |
Agentic & Tool Use Too close to call
Gemini 3 Flash Preview: 38.7 (#29), GPT-5.1-Codex: 38.0 (#33)
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| Terminal-Bench | 64.3% | 60.4% |
| τ²-bench Airline | 82.5% | — |
| τ²-bench Banking | 27.3% | — |
| τ²-bench Retail | 76.8% | — |
| τ²-bench Telecom | 91.2% | — |
| DeepResearch Bench | 49.8% | — |
| BALROG | 48.1% | — |
| GDP.pdf | 10% | — |
| LMArena Search | 1198 | — |
| METR Time Horizons | — | 70.8% |
| Vending-Bench 2 | 3,635 | — |
Reasoning Not comparable
Gemini 3 Flash Preview: 49.2 (#37), GPT-5.1-Codex: —
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| ARC-AGI-2 | 33.6% | — |
| SimpleBench | 61.1% | — |
| NYT Connections (extended) | 83.1% | — |
| ARC-AGI-1 | 84.7% | — |
| Chess Puzzles | 40% | — |
| LMArena Hard Prompts | 1465 | — |
| Mystery Game Puzzles | 26% | — |
| DTBench | 89.1% | — |
| LMCA | 43.1% | — |
| Epoch Capabilities Index | 151.8 | — |
| ForecastBench | 58.5 | — |
Math Gemini 3 Flash Preview leads
Gemini 3 Flash Preview: 51.7 (#55), GPT-5.1-Codex: 30.3 (#235)
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| ProofBench | 15% | 9% |
| FrontierMath (Tiers 1-3) | 51.2% | — |
| FrontierMath Tier 4 | 17.1% | — |
| MathArena Final-Answer Competitions | 67.6% | — |
| OTIS Mock AIME 2024-2025 | 95.6% | — |
| LMArena Math | 1473 | — |
| FrontierMath (Feb 2025 set) | 35.6% | — |
| FrontierMath Tier 4 (v1) | 4.2% | — |
Knowledge Not comparable
Gemini 3 Flash Preview: 58.8 (#33), GPT-5.1-Codex: —
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| GPQA Diamond | 89.4% | — |
| SimpleQA Verified | 66.8% | — |
| Vectara Hallucination Rate | 13.5% | — |
| LMArena Expert | 1462 | — |
Multimodal Not comparable
Gemini 3 Flash Preview: 45.5 (#16), GPT-5.1-Codex: —
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| LMArena Vision | 1285 | — |
| GeoBench | 88% | — |
| VPCT | 72.6% | — |
| Blueprint-Bench 2 | 0% | — |
| LMArena Document | 1413 | — |
Multilingual Not comparable
Gemini 3 Flash Preview: 55.7 (#27), GPT-5.1-Codex: —
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| LMArena Non-English | 1458 | — |
| LMArena Chinese | 1511 | — |
| LMArena French | 1477 | — |
| LMArena German | 1497 | — |
| LMArena Japanese | 1489 | — |
| LMArena Korean | 1443 | — |
| LMArena Russian | 1480 | — |
| LMArena Spanish | 1469 | — |
Instruction Following Not comparable
Gemini 3 Flash Preview: 75.7 (#56), GPT-5.1-Codex: —
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| LMArena Instruction Following | 1437 | — |
Long Context Not comparable
Gemini 3 Flash Preview: 44.4 (#67), GPT-5.1-Codex: —
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| LMArena Longer Query | 1452 | — |
Writing & Preference Not comparable
Gemini 3 Flash Preview: 65.5 (#45), GPT-5.1-Codex: —
| Benchmark | Gemini 3 Flash Preview | GPT-5.1-Codex |
|---|---|---|
| LMArena Text | 1466 | — |
| LMArena Creative Writing | 1457 | — |
| LMArena Multi-Turn | 1471 | — |
Frequently asked questions
Is Gemini 3 Flash Preview better than GPT-5.1-Codex?
Gemini 3 Flash Preview is the stronger model overall, scoring 52.3 to 38.6 on the Noometry Index.
Which is cheaper, Gemini 3 Flash Preview or GPT-5.1-Codex?
Gemini 3 Flash Preview is cheaper. It lists at $0.50 per million input tokens and $3 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.
Is Gemini 3 Flash Preview or GPT-5.1-Codex better for coding?
Gemini 3 Flash Preview scores higher on coding benchmarks: 50.9 versus 41.9 in the Noometry coding category.
Which has the bigger context window?
Gemini 3 Flash Preview does, with 1.05M tokens against 400K.
How many benchmarks do Gemini 3 Flash Preview and GPT-5.1-Codex share?
5 benchmarks have published results for both models. Gemini 3 Flash Preview has 59 scored results on Noometry and GPT-5.1-Codex has 6.