markup-validator

Check the markup validity of HTML, CSS and SVG files using the W3C validator

markup-validator takes HTML, CSS and SVG files and returns detailed validation results.

Installation

Install package for Node.js:

pnpm add --save-dev markup-validator

You can also install it using npm:

npm install --save-dev markup-validator

Usage

Options

files

Type: array
CLI arguments: -f <space-separated list of files>, --files <space-separated list of files>

Specifies which files to be sent to validation. This option takes precedence over the other options.

paths

Type: array
CLI arguments: -p <space-separated list of paths>, --paths <space-separated list of paths>

Specifies which folders or files to be sent to validation. When omitted, all files are validated (skipping the node_modules folder), unless the exclude option is specified.

exclude

Type: array CLI arguments: -e <space-separated list of paths>, --exclude <space-separated list of paths>

Lists strings to match in paths to skip. When omitted, all files specified by files options if defined (all files otherwise) are validated (skipping the node_modules folder).

languages

Type: array
Default: ["html", "css", "svg"] CLI arguments: -l <space-separated list of languages>, --languages <space-separated list of languages>

Specifies which languages to validate. When omitted, all languages are validated.

dryRun

Type: boolean
Default: false CLI arguments: -d, --dry-run

Bypasses the validation (for usage while building CI).

ignoreLevel

Type: "info", "warning" or null
Default: null
CLI arguments: -i <level>, --ignore-level <level>

Skips unwanted messages. When set to "warning", both the "info" level and the "warning" level are skipped.

CLI

markup-validator can be used as a CLI tool.

markup-validator [flags]

package.json scripts

You can run markup-validator from the scripts section of your package.json file.

{
  "scripts": {
    "validate-html": "markup-validator --languages html",
    "one-folder": "markup-validator --paths docs",
    "one-file": "markup-validator --files docs/index.html",
    "all-files": "markup-validator"
  }
}

Examples

• markup-validator: validates all HTML, CSS and SVG files in the project;
• markup-validator --paths docs --exclude build tmp: validates all HTML, CSS and SVG files in the docs/ folder, except files which have build or tmp anywhere in their pathname or filename;
• markup-validator --files docs/index.html docs/style.css docs/icon.svg: validates only the specified files;
• markup-validator --languages html css: validates only HTML and CSS files in the project.

Application code

In addition to the CLI interface, markup-validator can be imported and called in ESM and TypeScript projects.

import { MarkupValidator } from "markup-validator";

const options = { files: ["docs/index.html"] };
const validator = new MarkupValidator(options);
const validate = await validator.validate();

Get help

• Stack Overflow

Copyright & licence

© 2026 Victor Brito — Released under the MIT licence.