SEO Page Inspector — On-page SEO Audit 作者： Vlad

SEO Inspector — a full on-page SEO audit of any page, in one click. Free, local, no account.

Open the popup on any website and get a clean, organized breakdown of the page's SEO: what's wrong, where it is, and how to fix it. Everything runs inside your browser.

What it will never do

🚫 No account, no sign-up, no paywall. There is no Pro version. Every feature is free for everyone.
🚫 No analytics, no telemetry, no trackers. Nothing is ever sent to the developer.
🚫 No permission to read every site. It works on the page you open it on (activeTab). Site access is asked only when you start a check that needs it — link checker, image checker, sitemap or hreflang validation — and you can say no.
🚫 No requests behind your back. Beyond the page you are on, it contacts a server only when you press a button; every case is listed in the privacy policy. The Domain tab sends nothing but the domain name to rdap.org / dns.google, and only when you open it.
🚫 No pop-up tabs while you work, no nag screens, no interruptions. After a feature update it opens its own changelog page once, so you can see what changed — nothing else, ever.

What it does

📋 Summary — An Indexability verdict with the exact reasons: robots meta, X-Robots-Tag header, canonical, and whether robots.txt blocks Googlebot from this URL. Title and Description with character count and their real width in pixels, measured in the font Google uses, so you see what actually gets truncated. Canonical, Author, Publisher, Lang, Charset, live counts of headings, images and links, and a Google result preview. Color-coded status dots, one-click copy buttons.

🚩 Issues — Every problem from every tab in one list: critical, warnings, and quieter notices. Click any item to jump to the tab that explains it.

🏷 Headers — All H1–H6 in document order, indented and color-coded. Flags skipped levels, empty headings, a first heading that isn't H1, more or fewer than one H1, repeated headings, headings hidden from readers and headings parked off-screen. Copy the outline as Markdown, plain text, HTML tags or a spreadsheet table.

🎯 On-page highlighting — Labels every heading right on the page, and does it intelligently: slides hidden in a carousel or text folded under "read more" don't get stray labels floating in empty space — the container gets one summary chip ("H4 ×22 · 11 unique"). Labels never cover the heading they name. Switch on the link layer to see every link colored by kind — internal, external, nofollow, sponsored, UGC, anchor, empty href — with a legend; after a link check, broken links turn red and redirects amber right where they sit. The image layer outlines pictures without ALT or TITLE.

📝 Content — Word count, unique words, water, stop words, sentences and average length, Flesch Reading Ease, Flesch–Kincaid grade, Gunning Fog. Top words and 2- and 3-word phrases with frequency, density, and whether each appears in your Title, Description and H1.

⚡ Speed — Live Core Web Vitals (LCP, INP, CLS, FCP, TTFB) and the whole load waterfall: DNS, TCP, TLS, request, response, DOM interactive / content loaded / complete, transfer size, request count, every resource slower than 300 ms — each with a verdict.

🌍 Hreflang — Every language alternate and the x-default check. Then the part most tools skip: press "Check alternates" and it fetches each alternate page and reads its own tags — does it link back, does it return an error, does it redirect, does its canonical point somewhere else? Google ignores a cluster whose pages don't point at each other; now you can see it.

🖼 Images — Totals without ALT and without TITLE with thumbnails, images shipped far larger than the space they fill (aware of Retina screens, so a correct 2× image is never flagged), and an on-demand check for broken and heavy files.

🔗 Links — Totals, internal vs. external, unique, nofollow, anchors, empty hrefs, links pointing at an anchor that doesn't exist. Click any number in the breakdown to open the list already filtered. The Link checker probes every link's HTTP status; filter by All / Internal / External / Nofollow / Issues and click a result to jump to that link on the page.

📣 Social — Open Graph and Twitter Card tags with image preview, exactly as social networks and messengers will render them.

🧩 Schema — JSON-LD parsed and validated against Google's rich-result rules: required and recommended fields per type. Missing fields come with a copy-paste-ready fix, added lines highlighted. If a node's url or mainEntityOfPage points at a different page — the classic copied-template mistake that makes Google attribute your markup elsewhere — you get a warning naming the field, and the exact line is highlighted in the JSON. Microdata and RDFa are detected too.

🌐 Domain — The full registrar record via RDAP (modern WHOIS): registrar, IANA ID, website, WHOIS server, abuse contact, registrant and country where not redacted, status codes, DNSSEC, and the creation, update and expiry dates. Live DNS records (A, AAAA, NS, MX, TXT) over DNS-over-HTTPS.

🛠 Tools — Which of 14 AI and search crawlers may fetch this URL under robots.txt (Googlebot, Bingbot, GPTBot, ClaudeBot, PerplexityBot, Google-Extended and more) with the rule that blocks each. llms.txt and llms-full.txt detection, technologies, HTTP response headers. A sitemap validator that starts from the Sitemap lines in robots.txt, follows sub-sitemaps and .gz files, reports URLs with errors or redirects, and tells you whether the page you're on is listed at all. A check of the http / https / www / bare variants of the URL — how many different addresses they end on. Shortcuts to Search Console, PageSpeed Insights, Rich Results Test, Facebook Debugger and the W3C validator.

📄 Export — Download the audit as JSON or CSV, or open a clean, printable report.

🔔 The icon speaks for itself — After a scan the toolbar icon shows the number of critical issues, a green tick when the page is clean, and a tooltip listing the problems — no click needed. Optionally (off by default, needs site access) it can count issues as soon as any page finishes loading.

🖱 Right-click menu — On a page: open it in Rich Results Test, PageSpeed Insights or the Schema validator; jump to robots.txt, the sitemap or llms.txt; run a site: search; check the page's history on Archive.org; copy the heading outline. On a link: check its HTTP status, including where a redirect lands. On selected text: find copies of it on Google, see whether it appears in the title, description and H1, or measure its length in pixels. Every item can be switched off in settings.

⚙ Settings that follow you — Interface language, theme, default tab, highlighting and menu preferences live inside the popup and sync across your computers when Firefox Sync is on. Keyboard shortcut Alt+Shift+S opens the extension.

🌗 Light & dark theme.

🗣 20 languages — English, Українська, Русский, Español, Deutsch, Français, Português, Italiano, Polski, Nederlands, Türkçe, Svenska, Bahasa Indonesia, Tiếng Việt, हिन्दी, বাংলা, ไทย, 한국어, 日本語, العربية and اردو, with full right-to-left support. Follows your browser language, switchable any time.

Why you'll like it

One click, instant — the full audit appears the moment the popup opens.
Sees what others miss — noindex in the X-Robots-Tag header, robots.txt rules per crawler, hreflang that doesn't link back, schema that points at another page, headings hidden inside carousels.
Problems, not just data — an indexability verdict, a prioritized Issues list, color-coded warnings and highlighting on the page itself.
Accessible — full keyboard navigation and screen-reader support, WCAG AA contrast in both themes.
Private by design, and documented — the privacy policy lists every single request the extension can make, and when.
Free. No catch.

For SEO specialists, developers, content editors and site owners who want a fast, honest on-page audit without handing their browsing to anyone.