Summarizer: length property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

The length read-only property of the Summarizer interface returns the relative length of the generated summaries.

Value

An enumerated value specifying the relative length of the generated summaries, the exact nature of which depends on the Summarizer type value.

Possible values are:

A "short" summary

For type tldr and teaser, the summary should fit into one sentence.
For type key-points, the summary should be no more than three bullet points.
For type headline, the summary should be no more than 12 words.

A "medium" summary

For type tldr and teaser, the summary should fit into one short paragraph.
For type key-points, the summary should be no more than five bullet points.
For type headline, the summary should be no more than 17 words.

A "long" summary

For type tldr and teaser, the summary should fit into one paragraph.
For type key-points, the summary should be no more than seven bullet points.
For type headline, the summary should be no more than 22 words.

const summarizer = await Summarizer.create({
  length: "medium",
  // ...
});

// Logs "medium"
console.log(summarizer.length);

Specification
Writing Assistance APIs # dom-summarizer-length

	desktop					mobile							server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS	Deno	Node.js
`length` property Experimental	Chrome – Full support Chrome 138 (Release date: 2025-06-24) footnote footnote Availability may be subject to geographical restrictions.	Edge – No support Edge 138 (Release date: 2025-06-26) disabled disabled From version 138 users must explicitly set the `#edge-llm-summarization-api-for-phi-mini` preference to `Enabled`. To change preferences in Edge, visit about:flags.	Firefox – No support Firefox footnote No support	Opera – Full support Opera 122 (Release date: 2025-09-11) footnote footnote Availability may be subject to geographical restrictions.	Safari – No support Safari footnote No support	Chrome Android – No support Chrome Android footnote No support	Firefox for Android – No support Firefox for Android footnote No support	Opera Android – No support Opera Android footnote No support	Safari on iOS – No support Safari on iOS footnote No support	Samsung Internet – No support Samsung Internet footnote No support	WebView Android – No support WebView Android footnote No support	WebView on iOS – No support WebView on iOS footnote No support	Deno – No support Deno footnote No support	Node.js – No support Node.js footnote No support

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