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1.6.4 • Public • Published


node npm license Build Status

Wrapper for The Nu Html Checker (v.Nu)

js happiness style


You need install Java for working with node-w3c-validator Visit for download Java if you not have it

Table of Contents

  1. CLI
  2. Node.js API
  3. Errors and Warnings suppressing
  4. Changelog
  5. Contributing
  6. Code of Conduct


Install as global package

npm i -g node-w3c-validator


node-w3c-validator -i ./dist/*.html -f html -o ./reports/result.html -s

You may pass a glob pattern too

node-w3c-validator -i ./dist/**/*.html -f html -o ./reports/result.html -s


-i, --input <path>

Validate input path.

default: process.cwd()

--exclude <path>

Exclude from input path.

default: unset

-a, --asciiquotes

Specifies whether ASCII quotation marks are substituted for Unicode smart quotation marks in messages.

default: unset

-e, --errors-only

Specifies that only error-level messages and non-document-error messages are reported (so that warnings and info messages are not reported).

default: unset, all message reported, including warnings & info messages

-q, --exit-zero-always

Makes the checker exit zero even if errors are reported for any documents

-f, --format <format>

Specifies the output format for reporting the results

default: unset possible values: gnu | xml | json | text | html | lint

lint format is available from 1.4.0 version.
lint format is designed for convenient error output to the terminal.
it uses a eslint-formatter-pretty under the hood

lint format screenshot

--filterfile <filename>

Specifies a filename. Each line of the file contains either a regular expression or starts with "#" to indicate the line is a comment. Any error message or warning message that matches a regular expression in the file is filtered out (dropped/suppressed)

default: unset, checker does no message filtering

--filterpattern <pattern>

Specifies a regular-expression pattern. Any error message or warning message that matches the pattern is filtered out (dropped/suppressed)

default: unset, checker does no message filtering

-s, --skip-non-html

Skip documents that don’t have *.html, *.htm, *.xhtml, or *.xht extensions.

default: unset, all documents found are checked, regardless of extension

-H, --html

Forces any *.xhtml or *.xht documents to be parsed using the HTML parser.

default: unset, XML parser is used for *.xhtml and *.xht documents


Disables language detection, so that documents are not checked for missing or mislabeled html[lang] attributes.

default: unset, language detection & html[lang] checking are performed


Forces all documents to be be parsed in buffered mode instead of streaming mode (causes some parse errors to be treated as non-fatal document errors instead of as fatal document errors).

default: unset, non-streamable parse errors cause fatal document errors

-v, --verbose

Specifies "verbose" output. (Currently this just means that the names of files being checked are written to stdout.)

default: unset, output is not verbose

-V, --version

Shows the current version number.

-o, --output <path>

Write reporting result to the path

-b, --buffersize <size>

Increase maxBuffer size to prevent #3, !!! OUTPUT ERROR or Unexpected end of JSON input errors. This is because child_process stdout being truncated when validator check a lot of files.

CLI -b, --buffersize
# increase buffer size (1024 * 500) 
node-w3c-validator -i static/**/*.html -b 500
Node.js API exec.buffersize
// increase buffer size (1024 * 500)
nodeW3CValidator(validatePath, {
    format: 'html',
    exec: {
        buffersize: 1024 * 500
}, function (err, output) {
    // ...

Node.js API

Install in your project

npm i --save-dev node-w3c-validator

nodeW3CValidator(pathTo, options, done);


Name Data type Description
pathTo string The path to the folder or directly to the file, for verification, also it can be url to the Web document
options Object Options for validating, sеe description below
done Function Validation callback, sеe description below


You can use all available options from CLI / Options. Only change props name to the camelCase style, exeception --no-stream and --no-langdetect they must be declared without no part


  • --errors-only - errorsOnly: true
  • --no-langdetect - langdetect: false
  • --format json - format: 'json'

an exception

--buffersize 500

transforms to

exec: {
    buffersize: 1024 * 500

done(err, output)

Validation callback.


Name Data type Description
err Error / Object.<null> if no errors - will be null, else - Error object
output string string with reporting result, if no errors - can be as empty string

nodeW3CValidator.writeFile(filePath, outputData[, done])

Write file


Name Data type Argument Description
filePath string if no errors - will be null, else - Error object
outputData string / Buffer file output content
done Function optional if exist - it will asynchronous writes output to the filePath. See fs.writeFile(file, data, callback)

Usage Example

// imports
const nodeW3CValidator = require('node-w3c-validator');
// paths
const validatePath = './dist/*.html';
// or directly to the file - './dist/index.html'
// or a glob pattern - './dist/**/*.html'
const resultOutput = './reports/result.html';
// validate
nodeW3CValidator(validatePath, {
    format: 'html',
    skipNonHtml: true,
    verbose: true
}, function (err, output) {
    if (err === null) {
    nodeW3CValidator.writeFile(resultOutput, output);

Errors and Warnings suppressing

You can ignore some errors or warnings by suppressing them.
Note! This feature can be used only on html, json and lint formats.

You need to specify nodeW3Cvalidator field in your project package.json file.

Here can be two arrays, for errors (suppressErrors) and warnigns(suppressWarnings).
Values must be a string parts or fully value of "unwanted" message.
Under the hood - node-w3c-validator will use String.protorype.includes
method for filtering messages.

For example, you receive warning message:

The “type” attribute for the “style” element is not needed and should be omitted.

Now you can suppress it

  "nodeW3Cvalidator": {
    "suppressErrors": [],
    "suppressWarnings": [
      "The “type” attribute for the “style” element is not needed and should be omitted."


See Releases history


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Contributors 💪

Code of Conduct

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