# Gemini 3 Flash vs GPT-5.3 Codex

> Side-by-side benchmark comparison for Gemini 3 Flash and GPT-5.3 Codex across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gemini-3-flash-vs-gpt-5-3-codex
- Last updated: October 17, 2026

- Shared sourced benchmarks: 5
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Pick GPT-5.3 Codex if you want the stronger benchmark profile. Gemini 3 Flash only makes more sense when its price, context window, or workload-specific category wins matter more than the overall score.

## Summary

- GPT-5.3 Codex leads overall 60.48 to 54.28.
- The clearest category separation is in instruction following, where the averages are 66.1 for Gemini 3 Flash and 92.6 for GPT-5.3 Codex.
- The biggest single benchmark swing is Vibe Code Bench in Coding, with scores of 20.20% and 61.77%.
- Gemini 3 Flash is the cheaper option on output tokens, which matters if you expect large responses or heavy interactive use.
- Gemini 3 Flash also has the larger context window at 1M.

## Model Snapshot

| Property | Gemini 3 Flash | GPT-5.3 Codex |
|----------|----------|----------|
| Creator | Google | OpenAI |
| Type | Proprietary | Proprietary |
| Reasoning | Non-Reasoning | Reasoning |
| Context | 1M | 400K |
| Overall Score | 54.28 | 60.48 |
| Benchmarks Covered | 11 | 11 |
| Pricing (input/output) | $0.50 / $3.00 | $1.75 / $14.00 |

## Category Breakdown

### Agentic

- Winner: Directional only
- Gemini 3 Flash public-lane score: 32.4 (Supported · #88/128)
- GPT-5.3 Codex public-lane score: 55.5 (Estimated · #41/128)

| Benchmark | Gemini 3 Flash | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| Claw-Eval | 49.2% | Coming soon | Coming soon |
| Gert Labs | 56.63% | 57.47% | GPT-5.3 Codex |
| JobBench | 11.4% | 33.7% | GPT-5.3 Codex |
| Terminal-Bench 2.1 (Vals) | 53.9% | Coming soon | Coming soon |
| Terminal-Bench 2.0 | Coming soon | 77.3% | Coming soon |
| OSWorld-Verified | Coming soon | 64.7% | Coming soon |

### Coding

- Winner: GPT-5.3 Codex
- Gemini 3 Flash public-lane score: 32.1 (Supported · #88/150)
- GPT-5.3 Codex public-lane score: 53.5 (Supported · #35/150)

| Benchmark | Gemini 3 Flash | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| Vibe Code Bench | 20.20% | 61.77% | GPT-5.3 Codex |
| LiveCodeBench (Vals) | 85.6% | 87.3% | GPT-5.3 Codex |
| SWE-bench (Vals) | 75.0% | 78.0% | GPT-5.3 Codex |
| SWE-bench Verified | Coming soon | 85% | Coming soon |
| SWE-bench Pro | Coming soon | 56.8% | Coming soon |
| SWE-Rebench | Coming soon | 58.2% | Coming soon |
| Terminal-Bench 2.0 | Coming soon | 77.3% | Coming soon |

### Reasoning

- Winner: Not comparable
- Gemini 3 Flash public-lane score: 63.8 (Unranked · 2 rankable rows)
- GPT-5.3 Codex public-lane score: 83.1 (Unranked · 2 rankable rows)

### Multimodal & Grounded

- Winner: Not comparable
- Gemini 3 Flash public-lane score: 80.3 (Unranked · 1 rankable row)
- GPT-5.3 Codex public-lane score: 80.1 (Unranked · 1 rankable row)

### Knowledge

- Winner: Directional only
- Gemini 3 Flash public-lane score: 55.7 (Supported · #55/184)
- GPT-5.3 Codex public-lane score: 65.4 (Estimated · #33/184)

| Benchmark | Gemini 3 Flash | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| GPQA Diamond (Vals) | 87.9% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 88.6% | Coming soon | Coming soon |

### Instruction Following

- Winner: Directional only
- Gemini 3 Flash public-lane score: 66.1 (#76/148)
- GPT-5.3 Codex public-lane score: 92.6 (#18/148)

### Mathematics

- Winner: Not comparable
- Gemini 3 Flash public-lane score: 57.4 (Unranked · 2 rankable rows)
- GPT-5.3 Codex public-lane score: Coming soon

| Benchmark | Gemini 3 Flash | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | 51.228% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 17.073% | Coming soon | Coming soon |

## FAQ

### Which is better overall, Gemini 3 Flash or GPT-5.3 Codex?

GPT-5.3 Codex is ahead overall on BenchLM right now.

### Where is the biggest gap between Gemini 3 Flash and GPT-5.3 Codex?

The widest category gap is in instruction following, where the averages are 66.1 for Gemini 3 Flash and 92.6 for GPT-5.3 Codex.

### How many benchmarks does Gemini 3 Flash cover on BenchLM?

Gemini 3 Flash currently has 11 sourced benchmark scores on BenchLM.

### How many benchmarks does GPT-5.3 Codex cover on BenchLM?

GPT-5.3 Codex currently has 11 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Gemini 3 Flash vs GPT-5.3-Codex-Spark](/compare/gemini-3-flash-vs-gpt-5-3-codex-spark)
- [GPT-5.3 Codex vs GPT-5.3-Codex-Spark](/compare/gpt-5-3-codex-vs-gpt-5-3-codex-spark)
- [Gemini 3 Flash vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-gemini-3-flash)
- [GPT-5.3 Codex vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-gpt-5-3-codex)

## Explore More

- [Gemini 3 Flash profile](/models/gemini-3-flash)
- [GPT-5.3 Codex profile](/models/gpt-5-3-codex)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)