Model Comparison

Gemini 1.5 Flash vs GPT-5 CodexWhich is better in 2026?

Comparing Gemini 1.5 Flash and GPT-5 Codex across benchmarks, pricing, and capabilities.

Verdict: Gemini 1.5 Flash vs GPT-5 Codex — which is better?

Gemini 1.5 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.

Choose Gemini 1.5 Flash if…

  • you want predictable pricing at $0.15/M input and $0.60/M output

Choose GPT-5 Codex if…

  • you want the most recent training data — it shipped Sep 2025
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Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

Gemini 1.5 Flash and GPT-5 Codexdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Gemini 1.5 Flash specifies input context (1,048,576 tokens). Only Gemini 1.5 Flash specifies output context (8,192 tokens).

Google
Gemini 1.5 Flash
Input1,048,576 tokens
Output8,192 tokens
OpenAI
GPT-5 Codex
Input- tokens
Output- tokens
Thu Jun 25 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Gemini 1.5 Flash supports multimodal inputs, whereas GPT-5 Codex does not.

Gemini 1.5 Flash can handle both text and other forms of data like images, making it suitable for multimodal applications.

Gemini 1.5 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 1.5 Flash

Proprietary

Closed source

GPT-5 Codex

Proprietary

Closed source

Release Timeline

When each model was launched

Gemini 1.5 Flash was released on 2024-05-01, while GPT-5 Codex was released on 2025-09-15.

GPT-5 Codex is 17 months newer than Gemini 1.5 Flash.

Gemini 1.5 Flash

May 1, 2024

2.2 years ago

GPT-5 Codex

Sep 15, 2025

9 months ago

1.4yr newer

Knowledge Cutoff

When training data ends

Gemini 1.5 Flash has a knowledge cutoff of 2023-11-01, while GPT-5 Codex has a cutoff of 2024-09-30.

GPT-5 Codex has more recent training data (up to 2024-09-30), making it potentially better informed about events through that date compared to Gemini 1.5 Flash (2023-11-01).

Gemini 1.5 Flash

Nov 2023

GPT-5 Codex

Sep 2024

10 mo newer

Outputs Comparison

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Key Takeaways

Google
Larger context window (1,048,576 tokens)
Supports multimodal inputs
OpenAI

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

GoogleGemini 1.5 Flash
OpenAIGPT-5 Codex
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Detailed Comparison

AI Model Comparison Table
Feature
Google
Gemini 1.5 Flash
OpenAI
GPT-5 Codex

FAQ

Common questions about Gemini 1.5 Flash vs GPT-5 Codex.

Which is better, Gemini 1.5 Flash or GPT-5 Codex?

Gemini 1.5 Flash (Google) and GPT-5 Codex (OpenAI) each have strengths in different areas. Compare their benchmark scores, pricing, context windows, and capabilities above to determine which fits your needs.

How does Gemini 1.5 Flash compare to GPT-5 Codex in benchmarks?

Gemini 1.5 Flash scores XSTest: 97.0%, FLEURS: 90.4%, HellaSwag: 86.5%, GSM8k: 86.2%, BIG-Bench Hard: 85.5%. GPT-5 Codex scores SWE-Bench Verified: 74.5%.

What are the context window sizes for Gemini 1.5 Flash and GPT-5 Codex?

Gemini 1.5 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 1.5 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 1.5 Flash and GPT-5 Codex?

Gemini 1.5 Flash is developed by Google and GPT-5 Codex is developed by OpenAI.

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