Model Comparison

Gemini 2.5 Flash vs GPT-5 CodexWhich is better in 2026?

GPT-5 Codex significantly outperforms across most benchmarks.

Verdict: Gemini 2.5 Flash vs GPT-5 Codex — which is better?

Gemini 2.5 Flash (by Google) and GPT-5 Codex (by OpenAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

Gemini 2.5 Flash outperforms in 0 benchmarks, while GPT-5 Codex is better at 1 benchmark (SWE-Bench Verified). GPT-5 Codex significantly outperforms across most benchmarks.

Choose Gemini 2.5 Flash if…

  • you want predictable pricing at $0.30/M input and $2.50/M output

Choose GPT-5 Codex if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
  • you want the most recent training data — it shipped Sep 2025

Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

Gemini 2.5 Flash outperforms in 0 benchmarks, while GPT-5 Codex is better at 1 benchmark (SWE-Bench Verified).

GPT-5 Codex significantly outperforms across most benchmarks.

Sun Jul 26 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Gemini 2.5 Flash specifies input context (1,048,576 tokens). Only Gemini 2.5 Flash specifies output context (65,536 tokens).

Google
Gemini 2.5 Flash
Input1,048,576 tokens
Output65,536 tokens
OpenAI
GPT-5 Codex
Input- tokens
Output- tokens
Sun Jul 26 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Gemini 2.5 Flash supports multimodal inputs, whereas GPT-5 Codex does not.

Gemini 2.5 Flash can handle both text and other forms of data like images, making it suitable for multimodal applications.

Gemini 2.5 Flash

Text
Images
Audio
Video

GPT-5 Codex

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

Gemini 2.5 Flash

Proprietary

Closed source

GPT-5 Codex

Proprietary

Closed source

Release Timeline

When each model was launched

Gemini 2.5 Flash was released on 2025-05-20, while GPT-5 Codex was released on 2025-09-15.

GPT-5 Codex is 4 months newer than Gemini 2.5 Flash.

Gemini 2.5 Flash

May 20, 2025

1.2 years ago

GPT-5 Codex

Sep 15, 2025

10 months ago

3mo newer

Knowledge Cutoff

When training data ends

Gemini 2.5 Flash has a knowledge cutoff of 2025-01-31, while GPT-5 Codex has a cutoff of 2024-09-30.

Gemini 2.5 Flash has more recent training data (up to 2025-01-31), making it potentially better informed about events through that date compared to GPT-5 Codex (2024-09-30).

Gemini 2.5 Flash

Jan 2025

4 mo newer
GPT-5 Codex

Sep 2024

Outputs Comparison

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Key Takeaways

Google
Larger context window (1,048,576 tokens)
Supports multimodal inputs
OpenAI
Higher SWE-Bench Verified score (74.5% vs 60.4%)
GoogleGemini 2.5 Flash
OpenAIGPT-5 Codex
Compare in Playground

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against Gemini 2.5 Flash and GPT-5 Codex side-by-side, then vote on the output you prefer.

Gemini 2.5 Flash
✓ Preferred
GPT-5 Codex
Open in Playground
AI Model Comparison Table
Feature
Google
Gemini 2.5 Flash
OpenAI
GPT-5 Codex

FAQ

Common questions about Gemini 2.5 Flash vs GPT-5 Codex.

Which is better, Gemini 2.5 Flash or GPT-5 Codex?

GPT-5 Codex significantly outperforms across most benchmarks. Gemini 2.5 Flash is made by Google and GPT-5 Codex is made by OpenAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does Gemini 2.5 Flash compare to GPT-5 Codex in benchmarks?

Gemini 2.5 Flash scores Global-MMLU-Lite: 88.4%, AIME 2024: 88.0%, FACTS Grounding: 85.3%, GPQA: 82.8%, MMMU: 79.7%. GPT-5 Codex scores SWE-Bench Verified: 74.5%.

What are the context window sizes for Gemini 2.5 Flash and GPT-5 Codex?

Gemini 2.5 Flash supports 1.0M tokens and GPT-5 Codex supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Gemini 2.5 Flash and GPT-5 Codex?

Key differences include multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes Gemini 2.5 Flash and GPT-5 Codex?

Gemini 2.5 Flash is developed by Google and GPT-5 Codex is developed by OpenAI.

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