How to Summarize a Long Text: Extractive Summaries and What They Miss

You have a long article, a report or a set of notes and not much time. A summary can tell you what matters, but it can also quietly leave out the one thing you needed. Understanding how a summarizer works shows you how far to trust it.

Two kinds of summary

• Abstractive summaries write new sentences, the way a person does. They can be smooth, but a system that writes can also invent details that were never in the text.
• Extractive summaries select existing sentences from the original and put them in order. They cannot invent facts, because every sentence is yours.

The Text Summarizer is extractive. That is a deliberate choice: you get a shorter version made only of sentences already in the text.

How the tool picks sentences

It scores each sentence by how many of the text's most frequent meaningful words it contains. Common words such as "the" and "of" are ignored. Sentences that contain many of the important recurring words score higher. It then keeps the top-scoring sentences in their original order, at a percentage you choose.

• The length is set as a share of the sentences, from 10 to 80 percent. The default is 30.
• The result shows how many sentences were kept out of the total and the word counts before and after.
• You can paste text or open a .txt file, and copy the summary.

Everything happens in your browser. Nothing you paste is uploaded.

What an extractive summary does well

• Articles and reports with a clear topic, where important sentences repeat the key terms.
• Quickly finding which parts of a long document are worth reading in full.
• Creating a first outline you can edit.

What it misses

• Sentences that depend on context. A kept sentence that starts with "However" or "This" may refer to something that was dropped.
• Important points that are stated only once. The score favours repeated terms, so a single critical sentence can be left out.
• Numbers, exceptions and warnings that appear in an unremarkable sentence.
• Tone and nuance. The selected sentences may read as a list of fragments.

A better workflow

1. Skim first. Read the headings and the first sentence of each section so you know the shape of the text.
2. Summarize at a generous length. Try 40 to 50 percent, then shorten if you need to. A short summary of a short text is not much of a summary.
3. Check what was dropped. Search the original for key numbers, names and dates, and confirm they are in your summary.
4. Edit it into your own words. Joining the sentences with connecting phrases makes a coherent summary.
5. Cite the source. A summary is still someone else's ideas, so credit the original.

Using summaries for study and work

A summary is most useful as a starting point. Read the summary first to decide whether the full text is worth your time, then read the original sections the summary points to. For study, rewrite the key sentences in your own words to remember them. For work, paste the summary into your notes with a link to the source, so you can find the detail again.

Related tools

• To rework wording, see how to paraphrase text without plagiarizing.
• To clean up a draft, the Grammar and Spelling Checker catches common slips.
• To change capitalisation, use the Case Converter.