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Spell-checking Markdown with cSpell

Though I haven't written much on this blog, I wanted to add some basic spell-checking to my posts. I looked up "spell-checking markdown" and found an article by TJ Addison that explained how to do this with a tool called cSpell (the backbone of the somewhat popular Code Spell Checker VSCode extension). Definitely check out TJ's article for a more in-depth explanation of cSpell and how to use it, but here I'll explain how I set it up for my Eleventy blog.

Using cSpell

You can use cSpell without installing it as a dependency by running it with npx:

npx cspell src/posts/**/*.md

But I opted for installing it permanently as a dev dependency and using an npm script to run it:

npm install cspell --save-dev
  // ...
  "scripts": {
  	// ...
  	"spell": "cspell src/posts/**/*.md"

Add a config file

cSpell allows multiple filenames for its configuration but I went with cspell.config.js for consistency with my other config files (like eleventy.config.js and tailwind.config.js).

To start, set the version to 0.2 (currently always 0.2) and the language to either en or en-GB (both are included by default).

module.exports = {
  version: '0.2',
  language: 'en',

There are over 26 other language dictionaries available, but I'm only writing in English so I didn't need to add any others.

An important step is to define specific words to exclude or flag. I told cSpell to ignore some 11ty-specific terminology and a few common developer brands and buzzwords.

  words: [
  flagWords: [],

In addition to the words property, you can also define dictionaries - just longer lists of words. I added a dictionary for my GitHub repositories to prevent those from being spell-checked if I ever write about them.

  dictionaries: ["repos"],
  dictionaryDefinitions: [
      { "name": "repos", "path": "./utils/dicts/repos.txt" },

Instead of manually updating my repos.txt dict, I wrote a script to fetch my repositories from the GitHub API and write them to the file.

#!/usr/bin/env node

const fs = require('fs');
const path = require('path');

function getRepos() {
const reposFile = path.join(\_\_dirname, './dicts/repos.txt');
const reposURL = '<USERNAME>/repos';

  (async () => {
  	const response = await fetch(reposURL);
  	const json = await response.json();

  	if (Array.isArray(json)) {
  		const repos = =>;
  		fs.writeFileSync(reposFile, repos.join('\n'));
  	} else {
  		console.log('Invalid response format:', json);


Running the script on Netlify

If you're using Netlify, you can run this script and the spell-check script during the build process by adding it to the build command in your netlify.toml file (or the GUI on Netlify's website):

command = "node ./utils/get-repos.js && npm run spell && npm run build"
Netlify build command

Finally, the config file allows you to define regular expression patterns to ignore. I added a few to ignore Markdown code fences and Nunjucks expressions.

  // ...
  ignoreRegExpList: ["nunjucksExpression", "markdownCodeBlock", "markdownInlineCode"],
  patterns: [
          name: "nunjucksExpression",
          pattern: /{%.*?%}/gis
          name: "markdownCodeBlock",
          pattern: /`{3}[\s\S]*?`{3}(?=\n|$)/gi
          name: "markdownInlineCode",
          pattern: /`[^`]*`/gi

I'm surprised that there isn't a pattern for Markdown code blocks by default; I was having issues with common JavaScript libraries and methods being flagged as typos. Additionally, I use a few custom shortcodes that kept getting flagged as a typo, so the nunjucksExpression pattern was a must.

Ignore words in frontmatter

The neat thing about cSpell is you can also define words to ignore per file, so if you only use a word once, you can just ignore it in that file. For example, you could ignore the word supercalifragilisticexpialidocious in just one file by adding cSpell:ignore supercalifragilisticexpialidocious as a comment at the top of the file:

tags: [...]
title: Magna voluptate officia cillum Lorem proident.
description: Cupidatat excepteur ullamco laboris in veniam qui officia tempor aliquip et commodo.
date: 2000-01-01
# cSpell:ignore supercalifragilisticexpialidocious

You don't have to put it in the frontmatter, but I like to keep my posts as clean & organized as possible and it looks nice there.

Let me know if you have any questions or suggestions!

On Eleventy