I built a free Blog SEO Checker

It actually compares your article to live SERP winners across content quality, on-page SEO, competitiveness and AI-search readiness — then spits out missing subtopics, long-tail keyword ideas, and title/meta suggestions you can copy. The UI is clean and focused (URL + optional keyword + Cloudflare verification), but the idea is familiar to anyone using Surfer/MarketMuse; the real question is how thorough the extraction and scoring logic are, and whether the free limits and methodology hold up for serious audits.