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Dom Size

Testing & Quality
dom-size

Dom Size is an Agent Skill for testing & quality published in the thedaviddias/Front-End-Checklist repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

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.

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How to use this skill

Bring this guide into your coding agent with a prompt tailored to the tool you use.

  1. Open your project in Codex.
  2. Copy and paste the prompt below.
  3. Review files and risks before approving any action.
Prompt to paste
Inspect the Agent Skill at https://github.com/thedaviddias/Front-End-Checklist/blob/HEAD/skills/dom-size/SKILL.md and all supporting files. Report provenance, permissions, scripts, dependencies, and security risks. Propose an exact installation into .agents/skills/dom-size, but wait for my approval before writing files or running scripts.

Copying this prompt does not install or run the skill. Review third-party files before use.

Reduce DOM size and complexity

An excessive DOM size increases memory usage, slows down style calculations, and makes layout reflows more expensive, leading to poor interaction performance.

Quick Reference

  • Keep total DOM nodes below 1,500
  • Avoid deep nesting (maximum depth < 32)
  • Use virtualization for long lists of elements

Check

Check the total number of DOM nodes and the maximum DOM depth using Lighthouse or Chrome DevTools.

Fix

Simplify the HTML structure, remove unnecessary wrapper elements, and implement virtualization for large lists.

Explain

Explain the performance impact of a large DOM tree on memory and rendering speed.

Code Review

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/en/rules/performance/dom-size