Key takeaways
- Deterministic rule engine, not an LLM reasoner — 251 audit rules across 20 categories as of v3.0 (up from 108 rules and 12 categories at the January 2026 launch), with Core Web Vitals measured via a real browser
- 280 stars, 37 forks, MIT license, TypeScript. Created January 23, 2026; v3.0.1 shipped May 6, 2026; ~2,800 npm downloads/month for @seomator/seo-audit as of June 2026
- Three surfaces from one codebase — a seomator CLI with five output formats (including LLM-optimized XML), an Electron desktop dashboard, and a SKILL.md that scopes Claude to Bash(seomator:*)
- Vendor-maintained by SEOmator with a single contributor; the repo doubles as a funnel to SEOmator's free web audit tool and $49–$279/month SaaS plans
FAQ
What is SEO Audit Skill?
An open-source website audit tool from SEOmator — packaged as a CLI, an Electron desktop app, and a Claude Code skill — that checks any site against 251 deterministic rules across 20 categories including SEO, performance, security, structured data, accessibility, and AI/GEO readiness.
How much does SEO Audit Skill cost?
The CLI, desktop app, and skill are free and MIT-licensed; SEOmator's hosted SaaS platform, which the repo funnels toward, runs roughly $49 to $279 per month per third-party reviews.
How does SEO Audit Skill work with Claude Code?
A SKILL.md restricts the agent to Bash(seomator:*) commands; Claude runs the npm-installed CLI with the LLM-optimized XML output format, then analyzes and prioritizes the findings — the audit itself is deterministic code, not model judgment.
How is SEO Audit Skill different from claude-seo?
claude-seo is a prompt-and-subagent architecture where the model performs the analysis, while SEO Audit Skill is a conventional rule engine the model merely invokes — more reproducible per-page checks, far less strategic breadth.
Executive Summary
SEO Audit Skill (repo seo-skills/seo-audit-skill, npm @seomator/seo-audit, CLI seomator) is the open-source audit engine behind SEOmator's commercial SEO platform, published as a TypeScript CLI, an Electron desktop app, and a Claude Code skill.[1][2] Its bet is the opposite of most entries in the SEO/GEO agent-skills category: instead of prompting a model to reason about a site, it runs 251 deterministic rules across 20 categories — Core SEO, performance, links, images, security headers, technical SEO, crawlability, structured data, JavaScript rendering, accessibility, content, and AI/GEO readiness among them — and hands the agent a scored, LLM-optimized report to interpret.[2] The GitHub description still advertises the launch-era 108 rules across 12 categories; the v3.0 README and SKILL.md document 251 rules across 20.[1][2]
The project is unambiguously vendor-owned marketing-grade open source: the seo-skills GitHub account was created the same day as the repo (January 23, 2026), describes itself as "part of our complex SEO software," hosts exactly one public repository, and has a single contributor; the README's first call-to-action points to SEOmator's free web audit tool.[1][3] Traction is modest but real — 280 stars, 37 forks, and roughly 2,800 npm downloads in the last month as of June 2026 — and development moved fast early (v1.0.0 to v3.0.0 between January 23 and February 12, 2026) before slowing to maintenance, with the most recent push on May 8, 2026 hardening the LLM reporter against indirect prompt injection.[1][4][5]
| Attribute | Value |
|---|---|
| Maintainer | SEOmator (GitHub account seo-skills; npm maintainer seomator)[1][4] |
| Created | January 23, 2026[1] |
| GitHub Stars | 280 (37 forks, 0 open issues) as of June 2026[1] |
| License | MIT[1] |
| Language | TypeScript[1] |
| Latest Release | v3.0.1 (May 6, 2026); last push May 8, 2026[4][1] |
| npm Downloads | ~2,800/month; ~8,400 total since launch, as of June 2026[5] |
Product Overview
The core loop: install the CLI from npm (npm install -g @seomator/seo-audit), run seomator audit <url>, and get a health score with prioritized issues, severity levels, affected URLs, and fix suggestions.[2] Crawl mode extends the audit across a site with configurable concurrency and cross-page checks (duplicate content, orphan pages, pagination); Core Web Vitals (LCP, CLS, FCP, TTFB, INP) are measured through the system's Chrome/Chromium rather than estimated.[2]
As an agent skill, the SKILL.md frontmatter declares allowed-tools: Bash(seomator:*) — the agent can only invoke the audited CLI, a deliberately narrow permission surface — and the --format llm flag emits XML designed to be piped straight into Claude for analysis and fix prioritization.[2] The skill is also distributed through third-party marketplaces such as LobeHub.[6]
Key Capabilities
| Capability | Description |
|---|---|
| 251-rule audit engine | 20 categories, e.g. Core SEO (19 rules), Performance (22), Security (16), Crawlability (18), Structured Data (13), Accessibility (12)[2] |
| Core Web Vitals | LCP, CLS, FCP, TTFB, INP via real browser measurement[2] |
| JS rendering analysis | Raw vs rendered DOM comparison for SPA/CSR sites, SSR detection[2] |
| AI/GEO readiness | Semantic HTML, AI bot access, llms.txt checks[2] |
| 5 output formats | Console, JSON, HTML, Markdown, LLM-optimized XML[2] |
| Crawl + history | Concurrent multi-page crawls; persistent SQLite storage with audit history[2] |
| CI/CD integration | Exit codes, JSON output, GitHub Actions and GitLab CI examples[2] |
Product Surfaces
| Surface | Description | Availability |
|---|---|---|
CLI (seomator) | Single-page and crawl audits, TOML config, presets | GA via npm[4] |
| Claude Code skill | SKILL.md scoped to Bash(seomator:*); LLM-format reports | GA[2] |
| Desktop app | Electron dashboard — live progress, score history, trend charts | Build from source[2] |
| Hosted web tool | SEOmator's free browser-based audit (proprietary funnel) | GA[3] |
Technical Architecture
Everything runs locally: a Node.js 18+ TypeScript codebase that crawls pages, stores results in SQLite with compression, and uses the system Chrome, Chromium, or Edge for Core Web Vitals and JavaScript-rendering checks — no API key, no account, and no data sent to SEOmator.[2] The repo ships SKILL.md, a claude.md, an .mcp.json, and a skill/ directory alongside the CLI and Electron sources, signaling agent-native packaging from the start.[1] The May 8, 2026 commit "security: harden LLM reporter against indirect prompt injection" addresses a real agent-era risk — audited web pages injecting instructions into the report an LLM will read.[1]
Key Technical Details
| Aspect | Detail |
|---|---|
| Deployment | Local CLI / desktop app; Node.js 18+; Chrome optional for CWV[2] |
| Model(s) | None built in — deterministic rules; LLM-optimized output for any agent[2] |
| Integrations | Claude Code skill, GitHub Actions/GitLab CI, TOML config, MCP config present[2][1] |
| Open Source | MIT; single repo, single contributor (aeelbeyoglu, 79 commits)[1] |
Strengths
- Deterministic and reproducible where competitors are probabilistic — 251 coded rules produce the same findings on every run, making it suitable for CI gates and score tracking in a category dominated by prompt-driven analysis.[2]
- Real measurement, not model guesswork — Core Web Vitals come from an actual browser, and raw-vs-rendered DOM comparison catches SPA indexing problems that HTML-only checkers miss.[2]
- Tight, auditable agent permission surface —
allowed-tools: Bash(seomator:*)is one of the narrower skill scopes in the category; the agent runs one CLI and reads its output.[2] - Security-conscious maintenance — prompt-injection hardening of the LLM reporter shipped May 2026, a threat most SEO skills do not acknowledge.[1]
- Fast early iteration with commercial backing — 108 rules to 251 rules and three major versions within three weeks of launch, maintained by a revenue-generating SEO vendor rather than a hobbyist.[1][4][2]
Cautions
- Single-contributor, vendor-account project — one maintainer with 79 commits, a GitHub account created the day of launch with one public repo, and zero open issues that reads more as low engagement than perfect health.[1]
- Marketing-funnel open source — the README's first link routes to SEOmator's proprietary free audit tool; the project's continued investment depends on its funnel value to the SaaS.[2][3]
- Momentum has cooled — after the January–February 2026 sprint to v3.0.0, the only activity through June has been a May npm republish fix and the prompt-injection patch.[4][1]
- Audit-only scope — no keyword research, content generation, backlink analysis, or strategy; it finds issues but the breadth competitors offer lives in SEOmator's paid platform instead.[2]
- Stale repo description — GitHub still advertises 108 rules/12 categories against the documented 251/20, a small but telling documentation-hygiene gap.[1][2]
- Parent-platform reliability complaints — Capterra reviewers of the SEOmator SaaS report its off-page analysis is "not completely reliable," relevant context for trusting the same vendor's rule judgments.[7]
What Developers Say
There is no Hacker News or Reddit discussion of the skill or CLI itself as of June 2026 — the only HN footprint for SEOmator is a 2015 Show HN for the SaaS (13 points, zero comments).[8] The ~2,800 monthly npm downloads show quiet usage without public commentary.[5] Independent sentiment exists only for the parent SEOmator platform:
"You get detailed audits that point out errors fast. Each issue is marked with suggested steps." — PRPosting's SEOmator review[9]
"The SEOmator free audit tool offers surface-level checks. It skips deep analysis and exports." — PRPosting's SEOmator review[9]
"SEOmator doesn't plug into tools like Ahrefs or Semrush. There's no sync with content systems." — PRPosting's SEOmator review[9]
Treat these as adjacent evidence: they assess the hosted platform, not the open-source CLI, which actually answers the "deep analysis and exports" criticism with crawl mode and five export formats.[2]
Pricing & Licensing
| Tier | Price | Includes |
|---|---|---|
| Open-source CLI / skill / desktop app | Free | Full 251-rule engine, crawl mode, all output formats, MIT license[2][1] |
| SEOmator SaaS — Lite | $49/month | 1 project, 1 login (per third-party review)[9] |
| SEOmator SaaS — Standard | $99/month | 5 projects, 3 users[9] |
| SEOmator SaaS — Advanced | $279/month | 15 projects, 5 users[9] |
Licensing model: MIT for the entire repo — CLI, skill, and Electron app; the hosted web tool and SaaS platform are proprietary.[1][3]
Hidden costs: None for the CLI itself; the desktop app must be built from source (no packaged installers published), and the project's documentation consistently nudges toward the paid SEOmator platform.[2]
Competitive Positioning
Direct Competitors
| Competitor | Differentiation |
|---|---|
| Claude SEO | The category's star leader (8K+ stars); 25 sub-skills and 18 subagents where the model does the analysis — vastly broader strategy coverage, but probabilistic where SEO Audit Skill is deterministic |
| GEO Optimizer Skill | GEO/AI-visibility specialist; SEO Audit Skill touches AI readiness in a handful of rules (llms.txt, AI bot access) but is fundamentally a technical-SEO auditor |
| Agentic-SEO-Skill | 88 Python evidence-collector scripts with LLM reasoning and confidence labels on top — a hybrid; SEO Audit Skill keeps the model entirely out of the measurement loop |
| Lighthouse / Screaming Frog | The non-agent incumbents; SEO Audit Skill's edge is agent-native packaging, LLM-format output, and SEO-specific rules beyond performance |
When to Choose SEO Audit Skill Over Alternatives
- Choose SEO Audit Skill when: you want reproducible, CI-friendly technical audits an agent can run and interpret, real Core Web Vitals measurement, and a minimal agent permission footprint.
- Choose Claude SEO when: you want full-stack SEO strategy — content, E-E-A-T, schema, local, e-commerce — and accept model-driven analysis.
- Choose GEO Optimizer Skill when: AI-engine visibility specifically is the goal rather than classical technical SEO.
Ideal Customer Profile
Best fit:
- Developers and agencies wiring SEO health checks into CI/CD or agent pipelines who need deterministic, diffable results[2]
- Claude Code users who want a site audit as a single scoped Bash skill rather than a sprawling prompt architecture
- Teams auditing JavaScript-heavy sites where raw-vs-rendered DOM comparison matters
Poor fit:
- Marketers wanting keyword research, content generation, or backlink strategy — that is the paid SEOmator platform or a competitor skill
- Organizations that require multi-maintainer, community-governed open source for anything load-bearing
- Buyers expecting a packaged desktop install — the Electron app is source-build only[2]
Viability Assessment
| Factor | Assessment |
|---|---|
| Financial Health | Backed by SEOmator, a long-running SEO SaaS — but as a marketing asset, not a product line[3][8] |
| Market Position | Mid-pack on stars (280) in the SEO/GEO skills category; differentiated as the deterministic option[1] |
| Innovation Pace | Front-loaded — v1.0 to v3.0 in three weeks, then maintenance-only since February 2026[4][1] |
| Community/Ecosystem | Thin — one contributor, no public discussion threads, listed on skill marketplaces[1][8][6] |
| Long-term Outlook | Tied to SEOmator's funnel economics; the MIT license means the rule engine survives even if the vendor loses interest[1] |
The healthiest signal is the steady ~2,800 downloads/month against zero marketing presence in developer communities — people are finding and using it quietly.[5][8] The structural question is incentive durability: vendor-funnel open source gets maintained exactly as long as it converts, and the post-February slowdown suggests the sprint phase is over.[1]
Bottom Line
SEO Audit Skill is the engineering-brained entry in the SEO/GEO agent-skills category: a real rule engine with real browser measurement that treats the LLM as a report reader, not an auditor. That makes it the most defensible choice for CI pipelines and reproducible technical audits — and the least interesting one for anyone who wants an agent to do SEO strategy. The vendor-funnel provenance and single-maintainer bus factor are the honest risks; the MIT license is the honest mitigation.
Recommended for: Deterministic technical audits in CI or agent workflows, JavaScript-rendering diagnostics, teams that distrust model-judged SEO findings.
Not recommended for: Full-stack SEO strategy, keyword/content work, or teams that need community-governed tooling with multiple maintainers.
Outlook: Watch whether maintenance continues past mid-2026, whether the desktop app gets packaged releases, and whether the stale 108-rule repo description gets corrected — small signals that will reveal how seriously SEOmator treats the open-source side.
Research by Ry Walker Research • methodology
Sources
- [1] seo-skills/seo-audit-skill GitHub Repository (API metadata)
- [2] SEO Audit Skill: SKILL.md and README
- [3] SEOmator Free SEO Audit Tool
- [4] @seomator/seo-audit on npm
- [5] npm downloads API: @seomator/seo-audit
- [6] LobeHub Skills Marketplace: seo-audit
- [7] Capterra: SEOmator Reviews
- [8] SEOmator mentions on Hacker News (Algolia search)
- [9] PRPosting: SEOmator Review — The Good, The Gaps, The Verdict