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, H1, H2s, meta description, and first paragraph into 1-gram, 2-gram, and 3-gram phrases.
2. Normalize deterministically: lowercase, remove locale-aware stop words, lemmatize or stem consistently, preserve product names, and keep intent modifiers such as "best", "pricing", "vs", "review", "template", and year.
3. Score sections separately: title/H1 highest, meta description and H2s medium, first paragraph supporting.
4. Select the top-scoring 2-3 word phrase as the primary keyword and 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 - Assign explicit intent labels such as informational, commercial, transactional, comparison, or troubleshooting. Include confidence and a one-sentence rationale, or use an embeddings workflow with a documented threshold.
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 and a dedicated local CLI wrapper that reads DATAFORSEO_LOGIN and DATAFORSEO_PASSWORD from the environment and emits JSON. Do not use WebFetch for DataForSEO POST calls and never expose Basic auth headers, login, password, or encoded credentials in prompts or reports. If no wrapper exists in the project, report SKIPPED: DataForSEO wrapper unavailable and run local mode.

Endpoints Used

Page Intersection - find keywords where multiple URLs rank:

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

{
  "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
}

The wrapper sends DataForSEO auth headers from environment variables and never prints them.

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
• Do not combine canonical and noindex casually. Use noindex only when removal from search is intended
• Link from the weaker page to the authority page

NOINDEX

When a page should be removed from search results but still exist for users.

• Confirm the page has no meaningful unique search demand or business value
• Keep it crawlable until the noindex directive is observed
• Do not use as the default duplicate-content fix

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
• API request failures: If DataForSEO returns an error, retry once within rate limits. If it still fails, switch to local mode for remaining URLs and report the failed endpoint without credentials
• Single-post directory: If only one blog post exists, report "Cannibalization analysis requires at least 2 posts" and exit gracefully