Disallows elements with duplicated ID

Rule ID:
no-dup-id
Category:
Document
Standards:
  • HTML5
Fixable:
No

The ID of an element must be unique within the document. When <template> is used the id within the template must be unique but can otherwise contain duplicates as it isn't attached to the document yet.

Rule details

Examples of incorrect code for this rule:

<div id="foo"></div>
<div id="foo"></div>
error: Duplicate ID "foo" (no-dup-id)
  1 | <div id="foo"></div>
> 2 | <div id="foo"></div>
    |          ^^^


1 error found.

Examples of correct code for this rule:

<div id="foo"></div>
<div id="bar"></div>

Options

This rule takes an optional object:

{
  "include": null,
  "exclude": null
}

include

If set only IDs matching one or more patterns in this array are checked for duplicates. Supports wildcard with * (e.g. foo-*) and regexp with /../ (e.g. /^foo-\d+$/).

exclude

If set IDs matching one or more patterns in this array are ignored. Supports wildcard with * (e.g. foo-*) and regexp with /../ (e.g. /^foo-\d+$/).

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