Validating HTML


Before you can install HTMLHint you will need to install NodeJS to be able to use Node Package Manager (NPM).

You can use HTMLHint to validate your HTML on your local machine.

To use HTMLhint from the command line you need to install it globally. Open the Terminal app and use the following command:

npm install htmlhint -g

Once you’ve installed HTMLhint you can run it by passing in a URL or a filename. You can also use it against localhost URLs if your server is running.

To use HTMLhint:

htmlhint http://localhost:3000

Example output from HTMLHint

L299 |... viewBox="0 0 13 17">
          ^ The attribute name of [ viewBox ] 
          must be in lowercase. (attr-lowercase)

Scanned 1 files, found 1 errors in 1 files (55 ms)

You can configure HTMLHint to ignore false positives such as viewBox not being lowercase.

Create a htmlhint.json file in your project and add your HTMLHint rules. For example:

  "attr-lowercase": ["viewBox"] // Ignore rule for viewBox only

Then use your config file when running HTMLHint:

htmlhint --config htmlhint.json http://localhost:3000

W3C Markup Validation Service

If your website is on a public URL you can use the W3C Markup Validation Service. If you need to validate HTML on your local machine HTMLHint is a better option.

To use the W3C Markup Validation Service, Put your URL in, configure your options and select ‘Check’.

Example output from W3C Markup Validation Service:

Error: An img element must have an alt attribute, except under certain conditions...

From line 7, column 1; to line 7, column 21

<img src="cat.jpg" />