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Gemini 3.8 Flash vs GPT 5.1 Codex

At a glance

Google's most intelligent Flash model, with significant gains over 3.7 Flash across software engineering, agentic tasks, and multi-step reasoning.

1.0M ctx$0.83/$4.13 per M

Previous-generation coding-optimized model for software engineering.

400K ctx$1.25/$10.00 per M
Demos
All demos

No shared demos for these models yet.

AI Output
All AI outputs

No captured outputs for these models yet.

Benchmarks
See rankings
Reasoning
CodingInsufficient data
AgenticInsufficient data
Sources:Epoch AI·OpenRouter· as of 2026-10-02
Cheaper52%
Reasoning & Knowledge
Graduate Science95.4%Factual Recall69.7%
Math
Competition Math98.9%
Reasoning
CodingInsufficient data
AgenticInsufficient data
ReasoningInsufficient data
MathInsufficient data
Sources:OpenRouter
Reasoning & Knowledge
Graduate Science—Factual Recall—
Math
Competition Math—
Specs
1.0M
Context
66K
Max output
Sep 2026
Released
400K
Context
128K
Max output
Nov 2025
Released
Capabilities
Vision
Audio
Reasoning
Vision
Audio
Reasoning
Pricing
Live pricing, shown before you run
Input34%$0.83/M tokens
Output59%$4.13/M tokens
Reasoning$4.13/M tokens
Cache read37%$0.08/M tokens
Cache write$0.04/M tokens
Image input$0.83/M tokens
Audio input$0.83/M tokens
Web search$0.01/search
Live pricing, shown before you run
Input$1.25/M tokens
Output$10.00/M tokens
Cache read$0.13/M tokens
Web search29%$0.01/search
Chat with Gemini 3.8 FlashGo to model
Chat with GPT 5.1 CodexGo to model
Frequently Asked Questions: Gemini 3.8 Flash vs GPT 5.1 Codex▼

Which is better, Gemini 3.8 Flash or GPT 5.1 Codex?

▼

Both Gemini 3.8 Flash and GPT 5.1 Codex are capable AI models. The best choice depends on your specific use case: consider pricing, context window, speed, and which capabilities (vision, reasoning, audio) you need.

Which is cheaper, Gemini 3.8 Flash or GPT 5.1 Codex?

▼

Gemini 3.8 Flash has a lower blended cost. Gemini 3.8 Flash: $0.83 input / $4.13 output. GPT 5.1 Codex: $1.25 input / $10.00 output.

Which has a larger context window, Gemini 3.8 Flash or GPT 5.1 Codex?

▼

Gemini 3.8 Flash has a larger context window: Gemini 3.8 Flash supports 1M tokens vs GPT 5.1 Codex at 400K tokens.

Do both Gemini 3.8 Flash and GPT 5.1 Codex support vision?

▼

Yes, both Gemini 3.8 Flash and GPT 5.1 Codex support vision/image input.

What are the key differences between Gemini 3.8 Flash and GPT 5.1 Codex?

▼

Gemini 3.8 Flash and GPT 5.1 Codex have similar overall capabilities. The main differences lie in pricing, context window size, and provider-specific strengths. Use this comparison page to review all metrics side by side.

Which model should I choose for my use case?

▼

If cost is your priority, choose the cheaper option. If you need the highest intelligence for complex tasks, pick the higher-scoring model. For long documents or codebases, choose the larger context window. You can try both Gemini 3.8 Flash and GPT 5.1 Codex for free on idapt.app to see which performs better for your specific needs.

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