Best LLM for Document Summarization

We tested the top models on research papers, legal docs, and long articles. Compare summarization quality across all models with LLMWise.

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Evaluation criteria

Key point extractionLength controlFaithfulnessMulti-document handlingStructured output

Claude Sonnet 4.5Anthropic

The best model for faithful, accurate summarization. Claude Sonnet 4.5's 200K context window can ingest entire books, and its summaries are the most faithful to source material with the fewest invented details.

200K context window handles book-length documentsLowest hallucination rate in summariesExcellent at structured, hierarchical summaries

Gemini 3 FlashGoogle

Fast and highly capable with long documents. Gemini 3 Flash offers a massive context window with fast processing, making it ideal for summarizing large batches of documents quickly and affordably.

Processes long documents at the fastest speedExcellent multimodal summarization including imagesMost cost-effective for batch summarization jobs

GPT-5.2OpenAI

Produces the most readable and well-structured summaries. GPT-5.2 excels at turning dense material into clear, engaging prose, making it the best choice when summaries need to be shared with non-expert audiences.

Most readable and polished summary outputStrong at adjusting detail level for different audiencesExcellent structured output for JSON summaries

DeepSeek V3DeepSeek

A cost-effective option for technical summarization. DeepSeek V3 handles scientific papers and technical documents well, extracting key findings and methodology details accurately at a low price point.

Strong at extracting technical details and findingsVery affordable for high-volume summarizationGood at maintaining logical structure in summaries

Mistral LargeMistral

Solid multilingual summarization capabilities. Mistral Large summarizes documents in multiple European languages without requiring translation, preserving nuance that machine translation often loses.

Summarizes directly in European languagesEfficient token usage keeps summaries conciseGood at cross-lingual document comparison

Our recommendation

Claude Sonnet 4.5 is the top choice for summarization when accuracy and faithfulness matter most, especially for legal, medical, or research documents. For high-volume batch processing, Gemini 3 Flash offers the best speed-to-quality ratio. Compare both on your documents using LLMWise.

Use LLMWise Compare mode to verify these rankings on your own prompts.

Common questions

Which LLM produces the most accurate summaries?

Claude Sonnet 4.5 produces the most faithful summaries with the fewest hallucinated or invented details. Its large context window means it can process entire documents without chunking, which further reduces information loss.

How can I test summarization quality across models?

LLMWise Compare mode lets you send the same document to multiple models and review their summaries side by side. This makes it easy to check which model captures the key points you care about and which misses critical details.

Can LLMs summarize very long documents?

Yes. Claude Sonnet 4.5 handles up to 200K tokens (roughly 150,000 words) in a single context window. Gemini 3 Flash also supports very long contexts. For documents exceeding these limits, LLMWise supports chunked summarization workflows.

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