Text Summarizer
Extractive summarization using TF-IDF sentence scoring. Identifies the most important sentences and condenses any article or document.
Artificial intelligence (AI) is transforming industries at an unprecedented pace.
The rise of large language models has democratized access to AI capabilities.
The question is not whether AI will change the world, but how we choose to shape that change.
Free online AI text summarizer that condenses articles and documents without hallucination
Reading long articles, research papers, or meeting transcripts takes time you often don't have. The AI Text Summarizer on AlteredIdea uses TF-IDF extractive summarization to identify the most important sentences in any document and condense them into a shorter version: all running locally in your browser, with no server calls and no risk of your content being stored or misused.
Unlike AI writing tools that paraphrase or generate new text, this tool is extractive: it only selects real sentences from your original document. That means the summary is always factually accurate and never invents content. The highlighted source view lets you verify exactly which sentences were chosen, giving you full transparency into why the summary looks the way it does. Adjustable length from 1 to 10 sentences gives you control over the level of compression.
Step-by-step guide
- 1Paste your text
Copy any article, report, email thread, or document and paste it into the Original Text panel. The tool works best with 3 or more sentences. - 2Set the summary length
Use the slider or quick-select buttons (1, 2, 3, 5, 7 sentences) to choose how many sentences you want in the summary. - 3Read the summary
The Summary panel updates automatically as you adjust the length. The most important sentences are selected and presented in their original order. - 4Check highlighted source sentences
The Source panel highlights exactly which sentences from the original text were chosen, so you can verify the summary is capturing the right ideas. - 5Copy the result
Click Copy to save the summary to your clipboard. The compression percentage shown tells you how much the text was reduced.
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Frequently Asked Questions
- How does the summarizer work?
- The tool uses extractive summarization with TF-IDF (Term Frequency-Inverse Document Frequency) sentence scoring. It identifies which sentences contain the most important terms relative to the full document and selects the top-N sentences as the summary, preserving their original order.
- What is extractive summarization?
- Extractive summarization selects actual sentences from the original text rather than generating new ones. This means the summary is always factually accurate: it never invents or paraphrases content. It's the same approach used by many search engine snippet generators.
- How is this different from ChatGPT summarization?
- ChatGPT uses abstractive summarization: it paraphrases and may hallucinate details. This tool uses extractive summarization, which only selects real sentences from your text. The output is always grounded in the original document with zero risk of fabricated content.
- Does this tool send my text to a server?
- No. All summarization logic runs in your browser using JavaScript. Your text is never transmitted to any server, making it safe for confidential documents, private research, or proprietary content.
- What types of documents work best?
- The tool works best with factual prose: news articles, research papers, business reports, meeting transcripts, and documentation. It is less effective for poetry, fiction, or very short texts (fewer than 3 sentences).
- What does the compression percentage mean?
- The compression percentage shows how much shorter the summary is relative to the original text by character count. For example, -80% means the summary is 80% shorter than the original.
- Why are the first and last sentences often included in the summary?
- The tool applies a small position boost to the first and last sentences of the document, because these positions typically contain thesis statements and conclusions. This reflects common journalistic and academic writing conventions.
- Can I summarize non-English text?
- The tool's stopword list is English-only, so scoring accuracy will be lower for other languages. The sentence selection still works mechanically for any language that uses sentence-ending punctuation, but results will be less accurate.
- How many sentences should I target for a good summary?
- For most articles (500-1500 words), 3-5 sentences gives a solid overview. For longer documents or research papers, 5-7 sentences may be appropriate. Use the highlighted source view to check whether the selected sentences cover all the key points.
AlteredIdea vs alternatives
vs ChatGPT / LLM APIs: LLMs can hallucinate or alter facts when summarizing. AlteredIdea uses extractive summarization: only real sentences from your document, zero risk of fabricated content.
vs browser extensions: No install, no permissions, works on any device.
vs paid tools: Completely free, no account required.