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LLM ComparisonGPT-5.1Gemini 1.5 Flash

GPT-5.1 vs Gemini 1.5 Flash

Compare GPT-5.1 and Gemini 1.5 Flash. Build AI products powered by either model on Appaca.

Model Comparison

FeatureGPT-5.1Gemini 1.5 Flash
ProviderOpenAIGoogle
Model Typetexttext
Context Window400,000 tokens1,000,000 tokens
Input Cost
$1.25/ 1M tokens
$0.07/ 1M tokens
Output Cost
$10.00/ 1M tokens
$0.30/ 1M tokens

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Strengths & Best Use Cases

GPT-5.1

OpenAI

1. Configurable Reasoning for Agentic Tasks

  • Built to excel in autonomous or semi-autonomous coding workflows, with adjustable reasoning effort for planning, refactoring and debugging.

2. Fast Multi-Modal Input with Large Output

  • Accepts both text and image inputs while producing text outputs.
  • Offers up to 128 k output tokens, allowing long responses and code generation across multiple files.

3. Large Context & Knowledge Cut-Off

  • 400 k token context window supports processing large codebases or documents.
  • Knowledge cut-off of Sep 30 2024 ensures familiarity with recent tools and frameworks.

4. Reasoning Token Support

  • Provides explicit support for reasoning tokens, enabling developers to fine-tune the balance between reasoning depth and speed.

Gemini 1.5 Flash

Google

1. Extremely fast and cost-efficient

  • Designed for ultra-low latency inference.
  • Handles high-throughput real-time applications and large-scale pipelines.

2. Strong multimodal capabilities

  • Accepts text, images, audio, video, and PDFs.
  • Efficient cross-modal understanding suitable for classification, extraction, and captioning.

3. Excellent for long-context tasks

  • Supports up to 1M tokens, enabling analysis of long documents, transcripts, and entire codebases.
  • Performs well on long-context translation and summarization.

4. Optimized for production workloads

  • Low operational cost and fast inference make it ideal for enterprise automation.
  • Great for chatbots, customer support systems, and background agent tasks.

5. High throughput with scalable rate limits

  • Flash variants support extremely high RPM for high-traffic environments.

6. Reliable performance on everyday tasks

  • Good at chat, rewriting, transcription, extraction, and structured reasoning.
  • More efficient than Pro for tasks that don't require deep reasoning.

7. Ideal for multimodal high-volume apps

  • Strong performance on captioning, OCR-style extraction, audio transcription, and video understanding.

8. Designed for developer workflows

  • Supports function calling, structured output, and integration with the Gemini API and Vertex AI.