RenderDiff - SEO Rendering Diff Checker — Tim Berlin

RenderDiff compares the initial HTML source code of any webpage with its JavaScript-rendered DOM — and highlights every SEO-relevant difference.

Modern websites rely heavily on client-side JavaScript to render content. Search engine crawlers may see a completely different page than what users see in their browser. RenderDiff makes these hidden differences visible.

What it checks:
• Title tag, meta description, meta robots, canonical URL
• H1 and heading hierarchy (H2–H6)
• Open Graph and Twitter Card meta tags
• Structured data (JSON-LD, Microdata, RDFa) with property-level diffs
• Internal and external link counts with added/removed detail
• Image counts and missing alt attributes
• Word count and body content changes
• Hreflang tags, meta viewport, DOM node count
• Render timing measurement

Key features:
• Score from 0–100 measuring rendering parity (not SEO quality)
• Three views: Summary table, detailed per-element cards, full source diff
• Technology detection: 200+ frameworks, CMS platforms, and JS libraries
• Render type classification: SSR, CSR, SSG, Islands, JS-Enhanced, Pre-Rendered
• Smart noise filtering: cookie banners, ads, chat widgets, A/B tests, personalization
• User-Agent simulation: Chrome Desktop, Chrome Mobile, Googlebot Desktop/Mobile, or custom
• Export: Copy to clipboard, JSON, CSV, PDF — for all three views
• Page overlay highlighting of changed elements directly on the scanned page

Privacy-first:
• All processing happens locally in your browser
• No data is sent to any external server
• No analytics, tracking, or telemetry
• No user accounts required
• Only one network request per scan: fetching the page URL you choose to scan

RenderDiff is built for SEO professionals, web developers, and technical auditors who need to verify that search engines see the same content as users.