# Gemini 1.5 Flash vs GPT-5.3 Codex

> Side-by-side benchmark comparison for Gemini 1.5 Flash and GPT-5.3 Codex across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gemini-1-5-flash-vs-gpt-5-3-codex
- Last updated: October 14, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Evidence is too thin for a benchmark verdict: Gemini 1.5 Flash and GPT-5.3 Codex share only 1 sourced benchmark row.

## Summary

- Only 1 shared sourced benchmark row is available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Gemini 1.5 Flash has the larger published context window at 1M.

## Model Snapshot

| Property | Gemini 1.5 Flash | GPT-5.3 Codex |
|----------|----------|----------|
| Creator | Google | OpenAI |
| Type | Proprietary | Proprietary |
| Reasoning | Non-Reasoning | Reasoning |
| Context | 1M | 400K |
| Independent public score (not head-to-head) | null | 59.84 |
| Benchmarks Covered | 5 | 11 |
| Pricing (input/output) | N/A | $1.75 / $14.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- GPT-5.3 Codex public-lane score: 55.2 (Estimated · #35/124)

| Benchmark | Gemini 1.5 Flash | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.0 | Coming soon | 77.3% | Coming soon |
| OSWorld-Verified | Coming soon | 64.7% | Coming soon |
| Gert Labs | Coming soon | 57.47% | Coming soon |
| JobBench | Coming soon | 33.7% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- GPT-5.3 Codex public-lane score: 54.5 (Supported · #31/149)

| Benchmark | Gemini 1.5 Flash | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Verified | 9.6% | 85% | GPT-5.3 Codex |
| 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 |
| Vibe Code Bench | Coming soon | 61.77% | Coming soon |
| LiveCodeBench (Vals) | Coming soon | 87.3% | Coming soon |
| SWE-bench (Vals) | Coming soon | 78.0% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- GPT-5.3 Codex public-lane score: 83.1 (Unranked · 2 rankable rows)

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- GPT-5.3 Codex public-lane score: 80.1 (Unranked · 1 rankable row)

| Benchmark | Gemini 1.5 Flash | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| MMMU | 58.3% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- GPT-5.3 Codex public-lane score: 65.3 (Estimated · #31/181)

| Benchmark | Gemini 1.5 Flash | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 50% | Coming soon | Coming soon |
| SimpleQA | 8.6% | Coming soon | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- GPT-5.3 Codex public-lane score: 92.6 (#18/128)

### Mathematics

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- GPT-5.3 Codex public-lane score: Coming soon

| Benchmark | Gemini 1.5 Flash | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| AIME 2025 | 14.7% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between Gemini 1.5 Flash and GPT-5.3 Codex?

Not yet. The models share only 1 sourced benchmark row, so this mirror reports the available measurements and metadata without naming a broad winner.

### What can I compare safely on this page?

Published pricing, context windows, model type, and individual shared benchmark rows are directly comparable. Independent overall scores and non-overlapping benchmark coverage are labeled separately and should not be read as a controlled head-to-head result.

## Related Comparisons

- [Gemini 1.5 Flash vs GPT-5.3-Codex-Spark](/compare/gemini-1-5-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 1.5 Flash vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-gemini-1-5-flash)
- [GPT-5.3 Codex vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-gpt-5-3-codex)

## Explore More

- [Gemini 1.5 Flash profile](/models/gemini-1-5-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)