Getting started

HTML-validate is an offline HTML5 validator.

Installation

Install using npm:

npm install --save-dev html-validate

Create .htmlvalidate.json:

{
  "extends": ["html-validate:recommended"]
}

Run with:

npm exec html-validate yourfile.html

Configuration

Configuration can be added to:

ESM configuration files are not currently supported.

Configuration files will be searched from the target file and up until either no more parent folders exist or "root": true is found.

extends

Configuration can be extended from bundled preset or shareable configurations.

{
  "extends": [
    /* bundled preset */
    "html-validate:recommended",

    /* npm package */
    "my-npm-package",

    /* plugin with custom preset */
    "my-plugin:custom",

    /* local file */
    "./file"
  ]
}

A list of bundled presets is available at the preset list. By default html-validate:recommended is used.

When using NPM packages and files each must export a valid configuration object. Plugins may create custom configuration presets by exposing one or more preset in the plugin declaration.

rules

{
  "rules": {
    "some-rules": "severity",
    "other-rule": ["severity", { "option": true }]
  }
}

Severity can be one of:

Some options takes optional parameters when using the form ["severity", OPTIONS].

See rules for a list of all available rules and options.

elements

For proper validation some metadata for each element is required, detailing in which context it can be used, allowed/disallowed attributes, etc. If elements is not specified it defaults to ["html5"] which is a bundled collection for all HTML5 elements.

{
  "elements": [
    "html5",
    "my-npm-package",
    "./file",
    {
      /* inline metadata */
    }
  ]
}

Each entry will try to load metadata from (search in following order):

  1. Named bundled metadata.
  2. NPM package with the same name.
  3. A local file, json or js. Path is relative to the configuration file.

An object can also be passed with inline metadata but it is highly recommended to write it to a separate file.

See elements metadata for details about writing your own metadata.

plugins

List of extra plugins to load. Can be either a NPM package or relative path to a local file, i.e. when writing custom rules inside the repository.

Plugins can contain additional rules.

See writing plugins for details about creating your own plugins.

{
  "plugins": ["my-fancy-plugin", "./local-plugin"]
}

transform

Transform input files to extract HTML chunks, e.g. extract templates from javascript sources. See transformers for details.

{
  "transform": {
    "^.*\\.vue$": "html-validate-vue"
  }
}

This will transform *.vue with the html-validate-vue NPM package. Use a relative path to use a local script (use <rootDir> to refer to the path to package.json, e.g. <rootDir>/my-transformer.js).

root

By default, configuration is search in the file structure until the root directory (typically /) is found:

By setting the root property to true the search is stopped. This can be used to prevent searching from outside the project directory or to use a specific configuration for a specific directory without loading project configuration.

For instance, if /home/project/.htmlvalidate.json contains:

{
  "root": true
}

Only the following files would be searched:

This also affects CLI --config and the API, e.g. when using --config with a configuration using "root": true will prevent any additional files to be loaded.

Inline configuration

Configuration can be changed inline using directive of the form:

<!-- [html-validate-ACTION OPTIONS -- COMMENT] -->

ACTION is an action such as enable, disable etc and OPTIONS is arguments to the action. Comment is optional but encouraged.

Multiple rules can be enabled/disabled at once by using a comma-separated list:

<!-- [html-validate-disable-next void-style, deprecated -- disable both rules] -->

Comments can be entered using both -- and : as delimiter:

<!-- [html-validate-disable-next deprecated -- justification for disabling] -->
<blink>Blinking text</blink>
<!-- [html-validate-disable-next deprecated: justification for disabling] -->
<blink>Blinking text</blink>

enable

<!-- [html-validate-enable element-permitted-content] -->

Enables a rule. If the severity is set to off it will be raised to error, i.e a previously disabled warning will remain a warning after enabling it again.

disable

<!-- [html-validate-disable deprecated] -->

Disable a rule for the rest of the file or until re-enabled using enable directive.

disable-block

<!-- [html-validate-disable-block attribute-allowed-values] -->

Disables a rule for a block of elements. All siblings and descendants following the directive will not trigger any errors.

<div>
  <button type="foo">Invalid button</button>
  <!-- [html-validate-disable-block attribute-allowed-values -- will be disabled until the parent div is closed] -->
  <button type="bar">Invalid but ignored</button>
  <button type="baz">Still ignored</button>
</div>
<button type="spam">Another invalid</button>
error: Attribute "type" has invalid value "foo" (attribute-allowed-values) at inline:2:17:
  1 | <div>
> 2 |   <button type="foo">Invalid button</button>
    |                 ^^^
  3 |   <!-- [html-validate-disable-block attribute-allowed-values -- will be disabled until the parent div is closed] -->
  4 |   <button type="bar">Invalid but ignored</button>
  5 |   <button type="baz">Still ignored</button>


error: Attribute "type" has invalid value "spam" (attribute-allowed-values) at inline:7:15:
  5 |   <button type="baz">Still ignored</button>
  6 | </div>
> 7 | <button type="spam">Another invalid</button>
    |               ^^^^


2 errors found.

disable-next

<!-- [html-validate-disable-next deprecated] -->

Disables the rule for the next element.

<!-- [html-validate-disable-next deprecated -- the next occurrence will not trigger an error] -->
<blink>This will not trigger an error</blink>
<blink>But this line will</blink>
error: <blink> is deprecated (deprecated) at inline:3:2:
  1 | <!-- [html-validate-disable-next deprecated -- the next occurrence will not trigger an error] -->
  2 | <blink>This will not trigger an error</blink>
> 3 | <blink>But this line will</blink>
    |  ^^^^^


1 error found.

Ignoring files

.htmlvalidateignore file

The .htmlvalidateignore file works similar to .gitignore, i.e. the file should contain a list of file patterns to ignore.

Similar to .gitignore if a line starts with / it matches from the current directory only, e.g /foo.html matches only foo.html in the current directory but not src/foo.html.