Measure the size and nesting of a page's DOM, the tree of HTML elements. Identify unnecessary wrappers and oversized lists, then simplify the structure or render only visible list items to reduce confirmed rendering costs.
Use when auditing slow page loads, heavy assets, or rendering delays related to Reduce DOM size and complexity. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.
Inspect a page's DOM, the tree formed by its HTML elements, and assess the load associated with its element count and nesting depth. This skill uses Lighthouse or Chrome DevTools for measurement and helps remove unnecessary wrapper elements or simplify the HTML structure. For long lists, it also considers virtualization: rendering only the items needed for display.
Use it when pages with many elements are slow to display or interact with, or when investigating how long lists affect memory use and rendering work. It helps identify the files or rendering steps responsible for problems and explains which measurement method was used to confirm the load.
Before recommending changes, confirm the cause of slow performance using DevTools, Lighthouse, or data from actual usage environments. The source gives fewer than 1,500 DOM elements and a maximum depth below 32 as guidelines. Improvements should follow measured results rather than element counts alone.
This overview was written by AI (OpenAI Codex) from the public SKILL.md. Check the original below for the exact behavior.
AI rated this skill on four points using only the contents of its SKILL.md. Stars and popularity are not taken into account.
The total counts each point as A = 25, B = 15, C = 5. Rated by AI (OpenAI Codex) as of Oct 23, 2026. Treat it as a guide and read the original before installing.
Review the instructions the agent will receive before you install.
An excessive DOM size increases memory usage, slows down style calculations, and makes layout reflows more expensive, leading to poor interaction performance.
Check the total number of DOM nodes and the maximum DOM depth using Lighthouse or Chrome DevTools.
Simplify the HTML structure, remove unnecessary wrapper elements, and implement virtualization for large lists.
Explain the performance impact of a large DOM tree on memory and rendering speed.
Review the routes, assets, and loading behavior that affect Reduce DOM size and complexity. Flag exact files, requests, or rendering steps that add unnecessary network, CPU, or layout cost, and describe the measurement method used to confirm the issue.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/performance/dom-size
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