Model Comparison

Gemini 3.1 Pro vs GPT-5 CodexWhich is better in 2026?

Gemini 3.1 Pro significantly outperforms across most benchmarks.

Verdict: Gemini 3.1 Pro vs GPT-5 Codex — which is better?

Gemini 3.1 Pro (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 3.1 Pro outperforms in 1 benchmarks (SWE-Bench Verified), while GPT-5 Codex is better at 0 benchmarks. Gemini 3.1 Pro significantly outperforms across most benchmarks.

Choose Gemini 3.1 Pro if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
  • you want the most recent training data — it shipped Feb 2026

Choose GPT-5 Codex if…

  • you are already invested in the OpenAI ecosystem
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Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

Gemini 3.1 Pro outperforms in 1 benchmarks (SWE-Bench Verified), while GPT-5 Codex is better at 0 benchmarks.

Gemini 3.1 Pro significantly outperforms across most benchmarks.

Mon Jun 08 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Gemini 3.1 Pro specifies input context (1,048,576 tokens). Only Gemini 3.1 Pro specifies output context (65,536 tokens).

Google
Gemini 3.1 Pro
Input1,048,576 tokens
Output65,536 tokens
OpenAI
GPT-5 Codex
Input- tokens
Output- tokens
Mon Jun 08 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Gemini 3.1 Pro supports multimodal inputs, whereas GPT-5 Codex does not.

Gemini 3.1 Pro can handle both text and other forms of data like images, making it suitable for multimodal applications.

Gemini 3.1 Pro

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 3.1 Pro

Proprietary

Closed source

GPT-5 Codex

Proprietary

Closed source

Release Timeline

When each model was launched

Gemini 3.1 Pro was released on 2026-02-19, while GPT-5 Codex was released on 2025-09-15.

Gemini 3.1 Pro is 5 months newer than GPT-5 Codex.

Gemini 3.1 Pro

Feb 19, 2026

3 months ago

5mo newer
GPT-5 Codex

Sep 15, 2025

8 months ago

Knowledge Cutoff

When training data ends

Gemini 3.1 Pro has a knowledge cutoff of 2025-01-31, while GPT-5 Codex has a cutoff of 2024-09-30.

Gemini 3.1 Pro 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 3.1 Pro

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
Higher SWE-Bench Verified score (80.6% vs 74.5%)
OpenAI

No standout differentiators in the data we have for this pair.

Detailed Comparison

AI Model Comparison Table
Feature
Google
Gemini 3.1 Pro
OpenAI
GPT-5 Codex

FAQ

Common questions about Gemini 3.1 Pro vs GPT-5 Codex.

Which is better, Gemini 3.1 Pro or GPT-5 Codex?

Gemini 3.1 Pro significantly outperforms across most benchmarks. Gemini 3.1 Pro 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 3.1 Pro compare to GPT-5 Codex in benchmarks?

Gemini 3.1 Pro scores t2-bench: 99.3%, LiveCodeBench Pro: 96.2%, GPQA: 94.3%, MMMLU: 92.6%, BrowseComp: 85.9%. GPT-5 Codex scores SWE-Bench Verified: 74.5%.

What are the context window sizes for Gemini 3.1 Pro and GPT-5 Codex?

Gemini 3.1 Pro 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 3.1 Pro 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 3.1 Pro and GPT-5 Codex?

Gemini 3.1 Pro is developed by Google and GPT-5 Codex is developed by OpenAI.

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