SEO Technical: Canonical

Guides canonical tag configuration to consolidate duplicate content and declare preferred URLs.

When invoking

On

first use

, if helpful, open with 1–2 sentences on what this skill covers and why it matters, then provide the main output. On

subsequent use

or when the user asks to skip, go directly to the main output.

Scope (Technical SEO)

Duplicate site versions

HTTPS vs HTTP; www vs non-www; trailing slash (/page vs /page/) — choose one, 301 redirect others

Duplicate content

Canonical tags; consolidate and 301 to preferred URL

Initial Assessment

Check for product marketing context first:

If

.claude/product-marketing-context.md

or

.cursor/product-marketing-context.md

exists, read it for site URL and language structure.

Identify:

Site URL

Base domain

Duplicate scenarios

Multi-language, query params, pagination, alternate URLs

Framework

Next.js, React, static, etc.

Canonicalization Methods (Choose by Scenario)

Method

When

Strength

301 redirect

Preferred; server can redirect

Strongest — permanent redirect

Canonical tag

Cannot redirect (e.g. params, pagination)

Strong — HTML signal

robots.txt

Block non-canonical paths

Weak — advisory only

Use 301 for HTTP→HTTPS, www variants, trailing slash. Use canonical for params, pagination, UTM.

When to Use Canonical

Multi-language

Each language version has its own canonical; use

hreflang

with canonical

Same content, multiple URLs

Params, pagination, tracking params, www vs non-www, trailing slash (/page vs /page/)

Self-referencing

Canonical should point to self or the preferred version

Avoid chain canonical

A→B→C is invalid

Rules

Rule

Note

Absolute URL

Include

https://

Consistency

Must match current page URL or the chosen preferred version

No chains

A→B→C is invalid

Implementation Patterns

Next.js (metadata)

export

const

metadata

=

{

alternates

:

{

canonical

:

"https://example.com/page-slug"

,

languages

:

{

zh

:

"https://example.com/zh/page-slug"

,

en

:

"https://example.com/page-slug"

,

"x-default"

:

"https://example.com/page-slug"

,

}

,

}

,

}

;

HTML (generic)

<

link

rel

=

"

canonical

"

href

=

"

https://example.com/page-slug

"

/>

Server Redirects (301)

Apache (.htaccess)

:

RewriteEngine On

RewriteCond %{HTTPS} off

RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

Nginx

:

return

301

https://

$host

$request_uri

;

Relationship to Other Technical SEO

Sitemap

URLs in sitemap should match canonical

IndexNow

Submit canonical URLs Output Format Canonical URL for each page type Implementation (metadata or HTML) Multi-language setup if applicable References : Alignify URL optimization ; Google Canonical