Blog Cannibalization - Keyword Overlap Detection

Detect when multiple blog posts compete for the same search keywords. Two modes: local-only analysis (default) and DataForSEO API mode for SERP-level data.

Two Modes

Mode	Flag	Cost	Data Source
Local	(default)	Free	File content analysis via Grep/Read
API	--api	~$0.01/call	DataForSEO Page Intersection + Ranked Keywords

Local mode works without any API keys. API mode requires DataForSEO credentials set as environment variables: DATAFORSEO_LOGIN and DATAFORSEO_PASSWORD.

Local Mode Workflow

Step 1: Scan Blog Files

Use Glob to find all content files in the target directory:

• Patterns: **/*.md, **/*.mdx, **/*.html
• Skip files in node_modules/, .git/, drafts/

Step 2: Extract Primary Keywords

For each file, read and extract keyword signals from:

• Title tag or H1 heading (highest weight)
• H2 headings (medium weight)
• First paragraph (supporting signal)
• Meta description if present in frontmatter

Primary keyword extraction method:

1. Tokenize title and H1 into 1-gram, 2-gram, and 3-gram phrases
2. Score each phrase by frequency across title + H2s + first paragraph
3. Select the top-scoring 2-3 word phrase as the primary keyword
4. Record secondary keywords from H2 headings

Step 3: Cluster by Similarity

Group posts into clusters using these matching rules (in priority order):

1. Exact match - identical primary keyword across 2+ posts
2. Stem match - same root word (e.g., "optimize" vs "optimization")
3. Semantic overlap - Claude determines that two keywords target the same search intent (e.g., "best CRM software" vs "top CRM tools 2026")
4. Subset match - one keyword contains another (e.g., "email marketing" vs "email marketing for startups")

Step 4: Score and Flag

For each cluster with 2+ posts, assess severity and generate a recommendation.

Step 5: Output Report

Display the results table and per-cluster recommendations.

API Mode Workflow (DataForSEO)

Requires the --api flag. Uses WebFetch to call DataForSEO endpoints.

Endpoints Used

Page Intersection - find keywords where multiple URLs rank:

POST https://api.dataforseo.com/v3/dataforseo_labs/google/page_intersection/live
Authorization: Basic <base64(login:password)>

{
  "pages": {
    "1": "https://example.com/post-a",
    "2": "https://example.com/post-b"
  },
  "language_code": "en",
  "location_code": 2840
}

Cost: ~$0.01 per call. Returns overlapping keywords with position, volume, CPC.

Ranked Keywords - get all keywords a single URL ranks for:

POST https://api.dataforseo.com/v3/dataforseo_labs/google/ranked_keywords/live

{
  "target": "https://example.com/post-a",
  "language_code": "en",
  "location_code": 2840
}

API Analysis Steps

1. Collect all published URLs from the user (or sitemap)
2. Run Ranked Keywords for each URL to build keyword profiles
3. Run Page Intersection for URL pairs that share keyword clusters
4. Calculate severity using the formula below
5. Output enriched report with search volume and position data

Severity Scoring

Four severity levels based on overlap signals:

Level	Criteria	Action Urgency
Critical	Same exact keyword, both pages in top 20	Immediate
High	Same keyword cluster, one page outranks the other	This week
Medium	Related keywords with partial SERP overlap	This month
Low	Semantic similarity but different confirmed intents	Monitor

Severity Formula (API Mode)

severity_score = overlap_count x avg_search_volume x (1 / position_gap)

Where:

• overlap_count = number of shared ranking keywords
• avg_search_volume = mean monthly volume of shared keywords
• position_gap = absolute difference in average ranking position (min 1)

Higher score = more urgent cannibalization problem.

Severity Heuristic (Local Mode)

Without SERP data, use a simplified scoring:

• Critical: Exact primary keyword match between posts
• High: Stem match on primary keyword, or 3+ shared H2 keywords
• Medium: Semantic overlap on primary keyword
• Low: Subset match only, or shared secondary keywords

Output Format

Summary Table

| Post A | Post B | Shared Keywords | Severity | Recommendation |
|--------|--------|-----------------|----------|----------------|
| /best-crm-tools | /top-crm-software | best crm, crm tools, crm software | Critical | MERGE |
| /email-tips | /email-marketing-guide | email marketing | High | DIFFERENTIATE |
| /seo-basics | /seo-for-beginners | seo basics, beginner seo | Critical | CANONICAL |
| /react-hooks | /react-state-mgmt | react, state | Low | NO ACTION |

Per-Cluster Detail

For each flagged cluster, provide:

• Both post titles and URLs
• Full list of overlapping keywords (with volume if API mode)
• Which post is stronger (more comprehensive, better structured)
• Specific recommendation with rationale

Recommendations

Four possible actions for each cannibalization cluster:

MERGE

When both pages are thin or cover the same intent with similar depth.

• Combine the best content from both into one comprehensive post
• 301 redirect the weaker URL to the merged post
• Preserve all internal links pointing to either URL

DIFFERENTIATE

When pages serve different intents but keyword targeting overlaps.

• Shift the primary keyword of the weaker post to a related long-tail
• Update the title, H1, and meta description to reflect the new focus
• Add internal links between the two posts to signal distinct topics

CANONICAL

When one post is clearly the authority and the other is a lesser duplicate.

• Add rel="canonical" on the weaker page pointing to the authority
• Consider noindexing the weaker page if it adds no unique value
• Link from the weaker page to the authority page

NO ACTION

When intent is genuinely different despite surface-level keyword similarity.

• Document the reasoning for future audits
• Monitor rankings quarterly for any position changes
• Re-evaluate if either post drops in rankings

Error Handling

• No blog files found: If the directory contains no .md, .mdx, or .html files, report "No blog files found in [directory]" and suggest checking the path
• DataForSEO credentials missing: In API mode, if credentials are not configured, fall back to local mode automatically and notify the user
• API rate limits: DataForSEO has per-minute rate limits. If a 429 response is received, wait and retry once. If it persists, switch to local mode for remaining URLs
• WebFetch failures: If a source URL is unreachable, skip it and note "Unable to verify - source unavailable" in the report
• Single-post directory: If only one blog post exists, report "Cannibalization analysis requires at least 2 posts" and exit gracefully