Model Comparison
Gemini 3 Flash vs GPT-5.1 Codex HighWhich is better in 2026?
Gemini 3 Flash significantly outperforms across most benchmarks. Gemini 3 Flash is 3.1x cheaper per token.
Verdict: Gemini 3 Flash vs GPT-5.1 Codex High — which is better?
Gemini 3 Flash (by Google) and GPT-5.1 Codex High (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 Flash outperforms in 1 benchmarks (AIME 2025), while GPT-5.1 Codex High is better at 0 benchmarks. Gemini 3 Flash significantly outperforms across most benchmarks.
On price, Gemini 3 Flash is roughly 3.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Gemini 3 Flash also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.
Choose Gemini 3 Flash if…
- you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
- cost matters — it's about 3.1x cheaper per token
- you process long inputs — it offers a 1,000,000 token context window
- you want the most recent training data — it shipped Dec 2025
Choose GPT-5.1 Codex High if…
- you want predictable pricing at $1.25/M input and $10.00/M output
Performance Benchmarks
Comparative analysis across standard metrics
Gemini 3 Flash outperforms in 1 benchmarks (AIME 2025), while GPT-5.1 Codex High is better at 0 benchmarks.
Gemini 3 Flash significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, Gemini 3 Flash ($0.50/1M tokens) is 2.5x cheaper than GPT-5.1 Codex High ($1.25/1M tokens).
For output processing, Gemini 3 Flash ($3.00/1M tokens) is 3.3x cheaper than GPT-5.1 Codex High ($10.00/1M tokens).
In conclusion, GPT-5.1 Codex High is more expensive than Gemini 3 Flash.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Gemini 3 Flash accepts 1,000,000 input tokens compared to GPT-5.1 Codex High's 400,000 tokens. GPT-5.1 Codex High can generate longer responses up to 128,000 tokens, while Gemini 3 Flash is limited to 65,536 tokens.
Input Capabilities
Supported data types and modalities
Both Gemini 3 Flash and GPT-5.1 Codex High support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Gemini 3 Flash
GPT-5.1 Codex High
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Gemini 3 Flash was released on 2025-12-17, while GPT-5.1 Codex High was released on 2025-11-12.
Gemini 3 Flash is 1 month newer than GPT-5.1 Codex High.
Dec 17, 2025
5 months ago
1mo newerNov 12, 2025
7 months ago
Knowledge Cutoff
When training data ends
Gemini 3 Flash has a documented knowledge cutoff of 2025-01-31, while GPT-5.1 Codex High's cutoff date is not specified.
We can confirm Gemini 3 Flash's training data extends to 2025-01-31, but cannot make a direct comparison without GPT-5.1 Codex High's cutoff date.
Jan 2025
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Provider Availability
Gemini 3 Flash is available from Google. GPT-5.1 Codex High is available from OpenAI.
Gemini 3 Flash
GPT-5.1 Codex High
Outputs Comparison
Key Takeaways
No standout differentiators in the data we have for this pair.
Detailed Comparison
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FAQ
Common questions about Gemini 3 Flash vs GPT-5.1 Codex High.