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DOM Size Inspector - Online Count & Warn for Performance

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DOM Size Inspector

Analyze HTML for excessive DOM size, depth, and performance bottlenecks

Google Lighthouse Aligned
Your data stays local — nothing is uploaded
Uses a CORS proxy. For best results, use Paste HTML for local/testing pages.
DOM Inspector Bookmarklet

Drag this link to your bookmarks bar, then click it on any website to instantly analyze its DOM.

🔍 Inspect DOM

⬆ Drag the button above to your browser's bookmarks bar

Works on any site — even those you don't control

Frequently Asked Questions

DOM (Document Object Model) size refers to the total number of nodes in a webpage's document tree. A large DOM — typically over 1,500 nodes — can significantly degrade performance by increasing memory usage, slowing down style calculations, and delaying layout reflows. Google Lighthouse flags pages with excessive DOM size as a performance issue because it directly impacts user experience, especially on lower-end devices.

Google recommends keeping your DOM under 1,500 nodes total, with a maximum depth of 32 levels, and no more than 60 child nodes per parent. Pages exceeding these thresholds often experience slower rendering, increased scripting overhead, and higher memory consumption. Our tool aligns with these Lighthouse benchmarks to help you identify problem areas quickly.

  • Lazy load content: Use infinite scroll or pagination instead of rendering thousands of items at once.
  • Avoid deep nesting: Flatten your HTML structure — avoid unnecessary wrapper divs.
  • Use CSS over JS-generated markup: Replace JavaScript-generated DOM elements with CSS pseudo-elements or styles where possible.
  • Audit third-party scripts: Many plugins and widgets inject large amounts of DOM content.
  • Virtualize long lists: Use virtual scrolling libraries for large tables or lists.

DOM depth measures how many levels of nested elements exist from the root <html> tag to the deepest leaf node. Excessive depth (over 32 levels) forces browsers to traverse more nodes during style recalculation and layout, slowing down rendering. Deep nesting also makes CSS selectors more expensive and your code harder to maintain.

Yes! You can analyze any HTML by pasting the source code into the Paste HTML tab. For live websites, use the Fetch URL tab (which uses a CORS proxy) or — most reliably — drag our Bookmarklet to your bookmarks bar. The bookmarklet runs directly on any page you visit, giving you instant DOM analysis without leaving the site.

Absolutely. All analysis happens entirely in your browser. HTML you paste is never uploaded to any server. For URL fetching, the request goes through a public CORS proxy solely to retrieve the HTML — no data is stored or logged by our tool. The bookmarklet runs 100% client-side on your machine.
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