# no-html

Disallow HTML tags.

## Background

By default, Markdown allows you to use HTML tags mixed in with Markdown syntax. In some cases, you may want to restrict the use of HTML to ensure that the output is predictable when converting the Markdown to HTML.

## Rule Details

This rule warns when it finds HTML tags inside Markdown content.

Examples of **incorrect** code for this rule:

```markdown
<!-- eslint markdown/no-html: "error" -->

# Heading 1

Hello <b>world!</b>
```

## Options

The following options are available on this rule:

* `allowed: Array<string>` - when specified, HTML tags are allowed only if they match one of the tags in this array. (default: `[]`)

    Examples of **incorrect** code when configured as `"no-html": ["error", { allowed: ["b"] }]`:

    ```markdown
    <!-- eslint markdown/no-html: ["error", { allowed: ["b"] }] -->

    # Heading 1

    Hello <em>world!</em>
    ```

    Examples of **correct** code when configured as `"no-html": ["error", { allowed: ["b"] }]`:

    ```markdown
    <!-- eslint markdown/no-html: ["error", { allowed: ["b"] }] -->

    # Heading 1

    Hello <b>world!</b>
    ```

* `allowedIgnoreCase: boolean` - when `true`, enables case-insensitive matching of HTML tag names against the `allowed` array described above. (default: `false`)

    Examples of **incorrect** code when configured as `"no-html": ["error", { allowed: ["DIV"], allowedIgnoreCase: false }]`:

    ```markdown
    <!-- eslint markdown/no-html: ["error", { allowed: ["DIV"], allowedIgnoreCase: false }] -->

    # Heading 1

    <div>Hello world!</div>
    ```

    Examples of **correct** code when configured as `"no-html": ["error", { allowed: ["DIV"], allowedIgnoreCase: true }]`:

    ```markdown
    <!-- eslint markdown/no-html: ["error", { allowed: ["DIV"], allowedIgnoreCase: true }] -->

    # Heading 1

    <div>Hello world!</div>
    <DIV>Hello world!</DIV>
    <DiV>Hello world!</DiV>
    ```

## When Not to Use It

If you aren't concerned with HTML tags, you can safely disable this rule.

## Prior Art

* [MD033 - Inline HTML](https://github.com/markdownlint/markdownlint/blob/main/docs/RULES.md#md033---inline-html)
* [MD033 - no-inline-html](https://github.com/DavidAnson/markdownlint/blob/main/doc/md033.md)