❌ By default, this rule reports illegal attributes of extension tags and HTML tags as errors.

Examples of correct code for { "illegal-attr": 2 }:

<poem data-foo="foo" />

<div itemscope itemtype="https://schema.org/Product"></div>

<div tabindex="0"></div>

<ol type="1"></ol>

<br xmlns:foo="1">

<link itemprop="url" href="https://example.com">

This option can be configured to specify the severity of an non-zero tabindex.

Examples of incorrect code for { "illegal-attr": [ 0, { "tabindex": 2 } ] }:

<br tabindex="1">

Examples of correct code for { "illegal-attr": [ 2, { "tabindex": 0 } ] }:

<br tabindex="1">

This option can be configured to specify the severity of unknown attribute names.

Examples of incorrect code for { "illegal-attr": [ 0, { "unknown": 2 } ] }:

<ref id="foo">Bar</ref>

<br accesskey="b">

<br foo="bar">

<poem data-mw="foo" />

<meta itemprop="name" content="foo" class="bar">

<div itemtype="https://schema.org/Product"></div>

Examples of correct code for { "illegal-attr": [ 2, { "unknown": 0 } ] }:

<ref id="foo">Bar</ref>

<br accesskey="b">

<br foo="bar">

<poem data-mw="foo" />

<meta itemprop="name" content="foo" class="bar">

<div itemtype="https://schema.org/Product"></div>

This option can be configured to specify the severity of invalid attribute values.

Examples of incorrect code for { "illegal-attr": [ 0, { "value": 2 } ] }:

<ol type="foo"></ol>

<br xmlns:foo="javascript:alert(1)">

<link itemprop="url" href="foo">

Examples of correct code for { "illegal-attr": [ 2, { "value": 0 } ] }:

<ol type="foo"></ol>

<br xmlns:foo="javascript:alert(1)">

<link itemprop="url" href="foo">