seo-migration-check

Installation

$npx skills add lionkiii/claude-seo-skills --skill seo-migration-check

Summary

The agent can audit old-to-new URL redirect chains, canonical tags, metadata, content volume, and schema preservation to catch SEO regressions during domain changes or relaunches. Invoke when a user needs to verify that a site migration didn't lose search equity or break critical on-page signals.

SKILL.MD

Site Migration SEO Validator

Validates redirect chains, canonical tags, metadata, and content preservation during site migrations.

Inputs

Either:

  • old and new: Two URLs for a single-page check (e.g., https://old.com/page https://new.com/page)
  • file: Path to CSV/text file with URL pairs, one per line: old_url,new_url

If file provided: Read it and process each line. Skip blank lines and lines starting with #. For large files (>50 URL pairs), process first 50 and note truncation.

Execution

For each URL pair, run checks a-f:

Check a: Redirect Chain Validation

Fetch old URL with WebFetch and follow redirects (track each hop):

  1. Record redirect type: 301 (permanent), 302 (temporary), 307, 308
  2. Count redirect hops
  3. Record final destination URL

Evaluate:

  • Final destination matches expected new URL: PASS — mismatch: FAIL
  • Redirect type is 301: PASS — 302/307: WARN (temporary redirects pass less link equity)
  • Hop count 1: PASS — hop count 2: WARN — hop count >2: FAIL (redirect chain too long)
  • Direct 200 on old URL (no redirect): FAIL (old page still live, not redirected)

Check b: Canonical Consistency

Fetch new URL, extract <link rel="canonical" href="..."> from <head>.

  • Canonical matches new URL exactly: PASS
  • Canonical missing: WARN (Google will infer, but explicit is better)
  • Canonical points to old URL: FAIL (critical — tells Google old is authoritative)
  • Canonical points to third URL: WARN

Check c: Title and Meta Preservation

Compare title and meta description between old URL (before redirect) and new URL. Note: old URL may already redirect, so if old URL is not directly fetchable, skip comparison and note.

If comparable:

  • Title: Extract both. Compare word overlap.

    • 70% word overlap: PASS

    • 40-70% overlap: WARN (may be intentional change)
    • <40% overlap: WARN with note ("significant title change — verify this was intentional")
  • Meta description: Extract both.
    • Present on both: PASS
    • Missing on new URL: WARN
    • Both missing: NOTE

Check d: HTTP Status

Verify new URL returns 200 OK:

  • 200: PASS
  • 301/302 (new URL also redirects): WARN with destination
  • 404: FAIL
  • 500/5xx: FAIL

Check e: Content Similarity

If both old and new pages are fetchable, compare word counts:

  • New page word count >= 80% of old: PASS
  • New page word count 50-80% of old: WARN (possible content reduction)
  • New page word count < 50% of old: FAIL (significant content loss) If old URL not directly fetchable (already redirects): skip and note.

Check f: Schema Preservation

Extract @type values from JSON-LD blocks on both pages.

  • Same schema types present: PASS
  • Schema types reduced: WARN (lost structured data)
  • Key schema missing on new (e.g., Product, Article, LocalBusiness): WARN
  • No schema on either: NOTE (not a regression)

Overall Per-URL Result

FAIL: any check is FAIL WARN: no FAILs but any check is WARN PASS: all checks PASS or NOTE

Output Format

## Migration Validation: [old URL] → [new URL]
(or: ## Migration Validation: [N] URL pairs from [filename])

### Summary

| Status | Count |
|--------|-------|
| PASS | N |
| WARN | N |
| FAIL | N |
| Total | N |

### Per-URL Results

| Old URL | New URL | Redirect | Canonical | Title | Meta | Status Code | Schema | Overall |
|---|---|---|---|---|---|---|---|---|
| /old | /new | 301✓ | PASS | PASS | WARN | 200 | PASS | WARN |

### Failed Items Detail

For each FAIL result, expanded information:

**[old URL] → [new URL]**
- Redirect: [issue description]
- Canonical: [issue description]
- [etc.]
- Recommended fix: [specific action]

### Recommendations

[Prioritized list of actions based on failures and warnings]

## Data Sources

- Live URL fetching via WebFetch
- Redirect chain analysis (following HTTP headers)