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GPT 5.1 Codex vs Gemini 3.8 Flash

At a glance

Previous-generation coding-optimized model for software engineering.

400K ctx$1.25/$10.00 per M

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
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
ReasoningInsufficient data
MathInsufficient data
Sources:OpenRouter
Reasoning & Knowledge
Graduate Science—Factual Recall—
Math
Competition Math—
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%
Specs
400K
Context
128K
Max output
Nov 2025
Released
1.0M
Context
66K
Max output
Sep 2026
Released
Capabilities
Vision
Audio
Reasoning
Vision
Audio
Reasoning
Pricing
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
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
Chat with GPT 5.1 CodexGo to model
Chat with Gemini 3.8 FlashGo to model
Frequently Asked Questions: GPT 5.1 Codex vs Gemini 3.8 Flash▼

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

▼

Both GPT 5.1 Codex and Gemini 3.8 Flash 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, GPT 5.1 Codex or Gemini 3.8 Flash?

▼

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

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

▼

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

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

▼

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

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

▼

GPT 5.1 Codex and Gemini 3.8 Flash 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 GPT 5.1 Codex and Gemini 3.8 Flash for free on idapt.app to see which performs better for your specific needs.

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