What is canonical-tag-audit?

A website audit that checks rel="canonical" tags, which tell search engines which page URL should represent duplicate or similar pages. It also checks the URLs those tags point to.

Use it to crawl a site or URL list, validate canonical URLs and their status, and produce an SEO report about duplicate-page consolidation problems.

It finds canonical tags that are missing, duplicated, contradictory, unreachable, redirecting, blocked from indexing, or formatted in ways that can weaken search-engine indexing.

canonical-tag-audit — Skill for Claude Code and Codex by JakeLabate

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add JakeLabate/Claude-SEO-Skills --skill canonical-tag-audit

Clone the repo

git clone --depth 1 https://github.com/JakeLabate/Claude-SEO-Skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/jakelabate/claude-seo-skills/canonical-tag-audit/github.svg)](https://agentmods.dev/skills/jakelabate/claude-seo-skills/canonical-tag-audit)

Your own site

<a href="https://agentmods.dev/skills/jakelabate/claude-seo-skills/canonical-tag-audit"><img src="https://agentmods.dev/badge/skills/jakelabate/claude-seo-skills/canonical-tag-audit/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/jakelabate/claude-seo-skills/canonical-tag-audit"><img src="https://agentmods.dev/badge/skills/jakelabate/claude-seo-skills/canonical-tag-audit.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 122 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,367 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00122	$0.01367
Opus 5	$0.00061	$0.00683
Sonnet 5	$0.00024	$0.00273
Haiku 4.5	$0.00012	$0.00137

Measured 12d ago against content hash 61f9b5d2bf41, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

canonical-tag-audit scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

The scan reads SKILL.md. This mod also ships 5 executable files (scripts/audit_canonicals.py, scripts/extract_canonicals.py, scripts/fetch_pages.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/canonical-tag-audit/SKILL.md · 125 lines

How it starts

The opening of the file, as written. The whole thing — 125 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Canonical Tag Audit

Audit a website's rel="canonical" tags and produce an actionable SEO report.

When to use this skill

Use this skill when the user asks to:

Audit, validate, or check rel="canonical" tags / canonicalization
Find pages with missing, duplicate, or conflicting canonicals
Find canonicals that point at dead, redirecting, or noindexed URLs
Diagnose duplicate-content consolidation problems
Verify canonicals are absolute, same-host, and https://

Inputs to collect

Before starting, confirm with the user:

Site URL or URL list — a live site root to crawl (auto-seeds from /sitemap.xml), or a text file of URLs with --url-list.
Scope — how many pages to crawl (default 500, cap with --max-pages).
Probing — whether to probe each canonical target's status/redirect/noindex (default on; --no-probe for a fast structural-only pass).

The indexable contract: a canonical should point at a final, canonical, indexable 200 URL — ideally the page itself. A canonical that 404s, redirects, or is noindexed breaks consolidation and can drop the page from the index.

Workflow

Step 1: Crawl and probe canonicals

Use scripts/extract_canonicals.py:

python3 scripts/extract_canonicals.py https://example.com --max-pages 500 --output canonical_inventory.json
# already crawled once (e.g. in a full SEO audit)? skip the crawl and reuse the shared cache:
# python3 scripts/fetch_pages.py https://example.com --output page_cache.json
# python3 scripts/extract_canonicals.py --from-cache page_cache.json --output canonical_inventory.json

It records each page's status, every in-page <link rel="canonical"> (raw href + resolved URL), the Link: rel="canonical" header, meta robots, and X-Robots-Tag, then probes each unique canonical target once for status, redirect, and noindex.

Step 2: Run the audit checks

Use scripts/audit_canonicals.py:

python3 scripts/audit_canonicals.py canonical_inventory.json --output audit_report.json

Read the full file on GitHub · 125 lines

Files

What ships with it

7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

12d ago First seen · 125 lines · 122 tokens per session scan A 61f9b5d2bf41

Subscribe to this mod's changes

canonical-tag-audit is a skill published in the GitHub repository JakeLabate/Claude-SEO-Skills (2 stars, last pushed 2mo ago), licensed MIT. It adds 122 tokens to every session and 1,367 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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