SEO Analyzer (SEO Readiness Checker)
Paste a page's HTML (or upload an .html file) to get a rule-by-rule readiness checklist covering title and meta description length, H1 usage, canonical tag, viewport, image alt text, Open Graph and Twitter Card tags, JSON-LD structured data, robots directives, and word count, plus an overall readiness score. There's also an optional 'fetch from URL' mode that routes the request through a public CORS proxy (corsproxy.io), since browsers can't otherwise read another site's HTML. That mode is the one exception to this tool's default privacy; pasting HTML directly stays the fully private default.
Reviewed by Riccardo Dal Cero, Economist & Consultant · Last updated September 27, 2026
How it works
- 1
Paste a page's HTML source (view-source: in your browser, or Ctrl+U), or use the optional URL-fetch mode.
- 2
The tool extracts title, meta description, headings, images, Open Graph/Twitter tags, JSON-LD, and links.
- 3
Each element is checked against a plain-language readiness rule and marked pass, warning, or fail.
- 4
Review the overall score and fix flagged items directly in your page's HTML.
A checklist, not a black box
Instead of collapsing everything into one mysterious 'SEO score,' this tool shows exactly which rule passed or failed and why, so you can act on it directly. Every check here is based on well-documented, stable SEO fundamentals rather than opaque heuristics.
Privacy-first by default, with an honest opt-in exception
Every other tool in this toolkit runs entirely on your device with zero network calls. This one is different by necessity - analyzing a live third-party page requires fetching it, and browsers can't do that across origins without help. The paste-HTML mode keeps things fully private (you already have the source in your browser); the URL-fetch mode is opt-in, clearly labeled, and uses a public proxy rather than any private key or account of ours.
Frequently asked questions
Why does 'Fetch from URL' need a proxy?
Browsers block a webpage's JavaScript from reading another site's raw HTML across origins unless that site explicitly opts in via CORS headers, which most sites don't for their homepage. Routing through a public CORS proxy (corsproxy.io) works around that restriction, but it means the URL and page content pass through that third-party service: the only place in this toolkit where that happens. Pasting HTML directly avoids this and is the default.
Is the readiness score a guarantee of good rankings?
No. This checks well-established on-page fundamentals (title/description length, heading structure, structured data, mobile viewport, etc.) that are worth getting right, but actual rankings depend on many factors this tool can't see - backlinks, competition, search intent match, page experience, and more.
Does it check Core Web Vitals or page speed?
No, that requires actually loading and measuring a live page (e.g. via Lighthouse or CrUX field data), which is a different kind of tool than a static HTML analysis. This tool focuses on markup-level on-page SEO signals.
Why regex-based HTML parsing instead of a full DOM parser?
It keeps every check pure, fast, and fully testable without a browser environment, and works identically whether you paste a full page or just a fragment. It's deliberately tolerant of messy real-world HTML rather than requiring well-formed markup.
What counts as a 'fail' versus a 'warning'?
A fail is something search engines are known to penalize or that breaks a core signal entirely (a missing title, a noindex robots directive, no viewport meta). A warning is a soft best-practice miss - like a title outside the typical safe length range, or a couple of images missing alt text - that's worth reviewing but isn't necessarily wrong for your specific page.
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