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no-duplicate-headings

Disallow duplicate headings in the same document.

Background

Headings in Markdown documents are often used in a variety ways:

  1. To generate in-document links
  2. To generate a table of contents

When generating in-document links, unique headings are necessary to ensure you can navigate to a specific heading. Generated tables of contents then use those links, and when there are duplicate headings, you can only link to the first instance.

Rule Details

This rule warns when it finds more than one heading with the same text, even if the headings are of different levels.

Examples of incorrect code for this rule:

<!-- eslint markdown/no-duplicate-headings: "error" -->

# Hello world!

## Hello world!

Goodbye World!
--------------

# Goodbye World!

Options

The following options are available on this rule:

  • checkSiblingsOnly: boolean - When set to true, the rule will only check for duplicate headings among headings that share the same immediate parent heading. Default is false.

Examples of correct code for this rule with checkSiblingsOnly: true:

<!-- eslint markdown/no-duplicate-headings: ["error", { checkSiblingsOnly: true }] -->

# Change log

## 1.0.0

### Features
### Bug Fixes

## 2.0.0

### Features
### Bug Fixes

In this example, the duplicate "Features" and "Bug Fixes" headings are allowed because they have different parent headings ("1.0.0" vs "2.0.0").

When Not to Use It

If you aren't concerned with autolinking heading or autogenerating a table of contents, you can safely disable this rule.

Prior Art