Optimize JavaScript bundle size
SkillFiles & storagejs-file-size is a skill that guides an AI agent through checking whether large JavaScript bundles actually cause slow pages before suggesting fixes. It is used when auditing slow page loads, heavy assets, or rendering delays related to Optimize JavaScript bundle size. The skill emphasizes verifying the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.
Use Optimize JavaScript bundle size in Claude, ChatGPT or Ahel Desktop
Free. Sign in, add Optimize JavaScript bundle size and connect your AI. About a minute.
Also: Claude Code · Cursor · Codex
Then ask your AI: use the Optimize JavaScript bundle size skill
Details
Instructions available. Your AI can read the instructions. Execution depends on the setup they require.
Account requirements not reviewed. Check the skill instructions before use; ahel provides instructions and does not run this skill.
No other account needed.
Have an AI agent that supports loading skills.
What your AI can do with it
- Audit slow page loads, heavy assets, and rendering delays
- Check whether large JavaScript bundles are the actual bottleneck
- Verify findings using DevTools, Lighthouse, or field data
- Ground bundle-size recommendations in measured evidence
Getting started
- Have an AI agent that supports loading skills.
- Add the js-file-size skill to the agent's available skills.
- Ask the agent to audit a slow page load or heavy asset using the skill.
- Provide DevTools, Lighthouse, or field data so the agent can verify the bottleneck before recommending changes.
What this skill tells your AI
The instructions your AI receives, as published by thedaviddias/front-end-checklist in skills/js-file-size/SKILL.md and read by ahel’s review.
Excessive JavaScript increases parse and execution time, especially on low-end devices, leading to sluggish user experiences and high data costs.
Quick Reference
- Keep individual JS bundles under 200KB (compressed)
- Large bundles delay Time to Interactive (TTI) and First Input Delay (FID)
- Use code-splitting and tree-shaking to reduce unused code
Check
Review the JavaScript bundle sizes and identify any files exceeding 200KB (Gzip/Brotli).
Fix
Implement code-splitting, tree-shaking, and dependency audits to reduce the size of the JavaScript bundles.
Explain
Explain how large JavaScript files impact the main thread and delay user interactivity (FID/TTI).
Code Review
Review the routes, assets, and loading behavior that affect Optimize JavaScript bundle size. 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/js-file-size
Signals
- GitHub stars
- 74k
- Forks
- 7k
- Last commit
- Oct 2026
Questions
- When should this skill be used?
- Use it when auditing slow page loads, heavy assets, or rendering delays related to Optimize JavaScript bundle size.
- Does it recommend fixes right away?
- No. It first verifies the actual bottleneck in DevTools, Lighthouse, or field data before any changes are recommended.
- What data sources does it work with?
- DevTools, Lighthouse, and field data are the verification sources it uses.
Advanced
- Item type
- skill
- Key
js-file-size- Source
- github.com/thedaviddias/front-end-checklist
github.com/thedaviddias/front-end-checklist