link-rel-canonical-require

A <link rel="canonical"> with non-blank href must be present in <head> tag.

Level: Error

Config value

true: enable rule
false: disable rule

The following patterns are not considered rule violations

<!-- Valid canonical link with absolute URL -->
<html><head><link rel="canonical" href="https://example.com/dresses/green-dresses"></head></html>

<!-- Valid canonical link with relative URL -->
<html><head><link rel="canonical" href="/dresses/green-dresses"></head></html>

<!-- Valid canonical link with query parameters -->
<html><head><link rel="canonical" href="https://example.com/dresses/green-dresses?color=green&size=m"></head></html>

<!-- Valid canonical link with fragment -->
<html><head><link rel="canonical" href="https://example.com/dresses/green-dresses#section1"></head></html>

The following patterns are considered rule violations

<!-- Missing canonical link -->
<html><head></head></html>

<!-- Empty href attribute -->
<html><head><link rel="canonical" href=""></head></html>

<!-- Whitespace-only href attribute -->
<html><head><link rel="canonical" href=" "></head></html>

<!-- Missing href attribute -->
<html><head><link rel="canonical"></head></html>

Why this rule is important

While it’s generally not critical to specify a canonical preference for your URLs, there are several reasons why you would want to explicitly tell search engines about a canonical page in a set of duplicate or similar pages:

Specify preferred URL: Tell search engines which URL you want people to see in search results
Consolidate signals: Help search engines consolidate signals from similar pages into a single, preferred URL
Simplify tracking: Get consolidated metrics for specific content across multiple URLs
Optimize crawling: Prevent search engines from wasting time crawling duplicate content