Project: retextjs/retext-readability

Package: retext-readability@7.2.0

  1. Dependents: 0
  2. retext plugin to check readability
  1. unified 181
  2. plugin 140
  3. retext 42
  4. retext-plugin 26
  5. reading 3
  6. readability 2


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retext plugin to check readability.


What is this?

This package is a unified (retext) plugin to check readability: whether your presumed target audience can read your prose. It applies Dale—Chall, Automated Readability, Coleman-Liau, Flesch, Gunning-Fog, SMOG, and Spache.

When should I use this?

You can use this plugin when you’re dealing with content that might be difficult to read to some folks, and have authors that can fix that content.

💡 Tip: I also made an online, editable, demo, similar to this project: wooorm.com/readability.


This package is ESM only. In Node.js (version 16+), install with npm:

npm install retext-readability

In Deno with esm.sh:

import retextReadability from 'https://esm.sh/retext-readability@8'

In browsers with esm.sh:

<script type="module">
  import retextReadability from 'https://esm.sh/retext-readability@8?bundle'


Say our document example.txt contains:

The cat sat on the mat

The constellation also contains an isolated neutron
star—Calvera—and H1504+65, the hottest white dwarf yet
discovered, with a surface temperature of 200,000 kelvin

…and our module example.js contains:

import retextEnglish from 'retext-english'
import retextReadability from 'retext-readability'
import retextStringify from 'retext-stringify'
import {read} from 'to-vfile'
import {unified} from 'unified'
import {reporter} from 'vfile-reporter'

const file = await unified()
  .process(await read('example.txt'))


…then running node example.js yields:

3:1-5:57 warning Unexpected hard to read sentence, according to 4 out of 7 algorithms readability retext-readability

⚠ 1 warning

The default target age is 16. You can pass something else, such as 6:

-  .use(retextReadability)
+  .use(retextReadability, {age: 6})

…then running node example.js again yields:

1:1-1:23 warning Unexpected hard to read sentence, according to 4 out of 7 algorithms readability retext-readability
3:1-5:57 warning Unexpected hard to read sentence, according to all 7 algorithms      readability retext-readability

⚠ 2 warnings


This package exports no identifiers. The default export is retextReadability.

unified().use(retextReadability[, options])

Check hard to read sentences.


Transform (Transformer).


Configuration (TypeScript type).



Each message is emitted as a VFileMessage, with source set to 'retext-readability', ruleId to 'readability', actual to the difficult sentence, and expected to an empty array.


This package is fully typed with TypeScript. It exports the additional type Options.


Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, retext-readability@^8, compatible with Node.js 16.


See contributing.md in retextjs/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.


MIT © Titus Wormer