On-Page HTML SEO Tag Auditor Online Free
Paste the full HTML source of any page and get an instant on-page SEO audit covering the tags that actually influence rankings and click-through: title, meta description, H1 structure, canonical URL, Open Graph cards, mobile viewport, image alt attributes, robots directives, heading hierarchy, and JSON-LD structured data. Every finding is graded as an error, warning, or passed check and rolled into a single 0–100 health score you can track release over release.
On-Page HTML SEO Tag Auditor In-Browser Workspace
Input data or select files to begin. 100% private, client-side execution with zero server transmission.
How to Use On-Page HTML SEO Tag Auditor
- Step 1: Open your page in a browser and press Ctrl+U (Cmd+U on Mac) to view the rendered source.
- Step 2: Select all with Ctrl+A / Cmd+A, copy, and paste the HTML into the audit textarea.
- Step 3: Optionally add the page URL for context, then click Analyze SEO Tags.
- Step 4: Review the health score card and the color-coded issue list — errors first, then warnings, then passed checks.
- Step 5: Fix the flagged tags in your template or CMS, re-paste, and re-run until the score is green.
About On-Page HTML SEO Tag Auditor
On-page SEO auditing checks the HTML elements that search engines and social platforms read before ranking or rendering a snippet. The title tag is the strongest on-page relevance signal and should land between about 30 and 70 characters so Google does not truncate it; the meta description is not a ranking factor but controls the snippet shown under your result, so 80 to 165 characters maximizes the space. Exactly one H1 declares the page topic, while H2 and H3 tags form the outline crawlers use for section relevance. A canonical link tag consolidates duplicate URLs (http vs https, trailing slash variants, query parameters) into one authoritative address. Open Graph tags (og:title, og:description, og:image) shape how the page looks when shared on Facebook, LinkedIn, and Slack — missing og:image alone can cut social click-through dramatically. The viewport meta tag is mandatory for mobile-first indexing, and alt text on images both satisfies accessibility requirements and lets image search understand the asset. A noindex robots directive is scored as an error because it silently removes the page from the index. Finally, JSON-LD blocks in application/ld+json scripts unlock rich results such as breadcrumbs, FAQs, and product stars. The scorer subtracts 20 points per error and 5 per warning from a base of 100, so four missing critical tags zero out the score — a deliberately harsh penalty that mirrors how quickly a page can fall out of contention when fundamentals are absent.
Frequently Asked Questions
Does this tool crawl my website?
No. Nothing is fetched from any server. You paste the HTML source yourself (View Source → Copy), and the audit runs entirely in your browser with DOMParser. Your markup never leaves your machine.
Why is my score lower than other SEO tools?
This scorer is intentionally strict: every missing critical tag (title, description, H1, viewport) costs 20 points and each warning costs 5. Commercial dashboards often weight categories differently or cap penalties, which inflates scores for the same page.
How long should my title and meta description be?
Aim for 30–60 characters for the title and 120–155 for the description. Google truncates titles around 600 pixels (roughly 60 characters) and descriptions around 920 pixels, so staying inside those bounds keeps the full snippet visible.
Is meta keywords still checked?
No. The meta keywords tag has been ignored by Google since 2009, so flagging it would create noise. The tool focuses on tags that still affect crawling, ranking presentation, or social sharing.
Can I audit pages behind a login?
Yes. Any HTML you can view with View Source can be pasted here — intranet pages, local dev servers, and staging environments all work because the analysis never needs network access.