AMP HTML validator (amp-validator)

> AMP HTML is a way to build web pages that render with reliable and
fast performance. It is our attempt at fixing what many perceive as
painfully slow page load times – especially when reading content on
the mobile web. AMP HTML is built on existing web technologies; an
AMP page will load (quickly) in any modern browser.

From [AMPProject - AMP HTML][ampproject]

Why is this important?

If you are building an AMP page, you need to make sure the HTML is
valid. Only valid AMP content can be added to an [AMP Cache][amp-cache].

What does the hint check?

This hint uses [amphtml-validator][amphtml-validator] to validate the
HTML of your page.

Can the hint be configured?

Yes, you can decide if you want to receive errors only, or also
warnings found by [amphtml-validator][amphtml-validator].
By default, all warnings and errors are reported. If you prefer to
see only the errors, you can use the following hint configuration
in your [.hintrc][hintrc] file:

``json
{
"connector": {...},
"formatters": [...],
"hints": {
"amp-validator": ["error", {
"errorsOnly": true
}],
...
},
...
}
`

How to use this hint?

To use it you will have to install it via npm:

`bash
npm install @hint/hint-amp-validator --save-dev
`

Note: The recommended way of running webhint is as a devDependency of
your project.

And then activate it via the [.hintrc][hintrc] configuration file:

`json
{
"connector": {...},
"formatters": [...],
"hints": {
"amp-validator": "error",
...
},
"parsers": [...],
...
}
``

Further Reading

* [What is AMP][amp]
* [How AMP Works][amp-works]

[amp-cache]: https://www.ampproject.org/docs/guides/how_cached
[amp-works]: https://www.ampproject.org/learn/about-how/
[amp]: https://www.ampproject.org/learn/overview/
[amphtml-validator]: https://www.npmjs.com/package/amphtml-validator
[ampproject]: https://github.com/ampproject/amphtml
[hintrc]: https://webhint.io/docs/user-guide/configuring-webhint/summary/