I Optimize
boussadjra/vuestrata
Improve interface performance across loading speed, rendering, animations, images, and bundle size.
A skill your agent uses when auditing slow page loads, heavy assets, or rendering delays related to Optimize JavaScript bundle size.
Install JS File Size
$ npx skills add thedaviddias/Front-End-Checklist --skill js-file-size -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install thedaviddias/Front-End-Checklist js-file-size --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/js-file-size .claude/skills/js-file-size && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "js-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/js-file-size into .claude/skills/js-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "js-file-size", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/js-file-sizeType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add thedaviddias/Front-End-Checklist --skill js-file-size -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install thedaviddias/Front-End-Checklist js-file-size --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/js-file-size .agents/skills/js-file-size && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "js-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/js-file-size into .agents/skills/js-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "js-file-size", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill js-file-size -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install thedaviddias/Front-End-Checklist js-file-size --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/js-file-size .cursor/skills/js-file-size && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "js-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/js-file-size into .cursor/skills/js-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "js-file-size", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/thedaviddias/Front-End-Checklist.git --path skills/js-file-size--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add thedaviddias/Front-End-Checklist --skill js-file-size -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install thedaviddias/Front-End-Checklist js-file-size --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/js-file-size .gemini/skills/js-file-size && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "js-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/js-file-size into .gemini/skills/js-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "js-file-size", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install thedaviddias/Front-End-Checklist js-file-sizeInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add thedaviddias/Front-End-Checklist --skill js-file-size -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/js-file-size .github/skills/js-file-size && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "js-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/js-file-size into .github/skills/js-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "js-file-size", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill js-file-size -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install thedaviddias/Front-End-Checklist js-file-size --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/js-file-size .opencode/skills/js-file-size && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "js-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/js-file-size into .opencode/skills/js-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "js-file-size", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
js-file-size- GitHub stars
- 74k
- Token cost
- ~408 tokens
- SKILL.md length
- 150 words
- Files
- 2 (incl. references)
- Skills in repo
- 390
- Repo updated
- First seen
- Licence
- MIT
At a glance
A skill your agent uses when auditing slow page loads, heavy assets, or rendering delays related to Optimize JavaScript bundle size.
- Auditing slow page loads
- SKILL.md covers Quick Reference, Check, Fix and Explain, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
- Rendering delays related to Optimize JavaScript bundle size
What it does
JS File Size is an agent skill from thedaviddias/Front-End-Checklist. Use when auditing slow page loads, heavy assets, or rendering delays related to Optimize JavaScript bundle size. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.
Its SKILL.md is about 410 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/rule.md`).
It sits in Frontend & Design, covering Web performance. It works with JavaScript. The repository describes itself as: 🗂 The essential checklist for modern web development, for humans and AI agents. The licence is MIT.
When your agent uses it
- Auditing slow page loads
- Rendering delays related to Optimize JavaScript bundle size
Example prompts
- “/js-file-size”
What it can do on your machine
Read from SKILL.md and the folder at commit e8d14d0. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
Links to these hosts (documentation or services it may open):
frontendchecklist.io
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
JS File Size loads about 408 tokens when it runs, and up to ~1k if it reads all its reference files. Until then it costs about 56 tokens; SKILL.md has 150 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from thedaviddias/Front-End-Checklist at commit e8d14d0, republished under its MIT licence (© thedaviddias). 150 words, ~408 tokens.
Download SKILL.mdSave it as
.claude/skills/js-file-size/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- js-file-size
- description
- Use when auditing slow page loads, heavy assets, or rendering delays related to Optimize JavaScript bundle size. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.
- metadata.category
- performance
- metadata.priority
- medium
- metadata.difficulty
- intermediate
- metadata.estimatedTime
- 10
- metadata.source
- frontendchecklist.io
- metadata.url
- https://frontendchecklist.io/rules/performance/js-file-size
Optimize JavaScript bundle size
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/rules/performance/js-file-size
© thedaviddias, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 1 other file (references) in skills/js-file-size of thedaviddias/Front-End-Checklist.
- SKILL.md
- references/rule.md
Open the folder on GitHubat commit e8d14d0
Compare with similar skills
JS File Size next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| JS File Size this skillthedaviddias/Front-End-Checklist | 74k | — | ~408 | Automated safety check: Pass | MIT | |
| I Optimizeboussadjra/vuestrata | 111 | 11 repos | ~1.9k | Automated safety check: Pass | MIT | |
| Compare Array Bundle SizePostHog/posthog-js | 634 | — | ~599 | Automated safety check: Pass | Custom licence | |
| Web Performancemozilla/firefox-devtools-mcp | 478 | — | ~1.2k | Automated safety check: Pass | Custom licence | |
| Igniteui Wc Integrate With FrameworkIgniteUI/igniteui-webcomponents | 170 | — | ~1.4k | Automated safety check: Pass | MIT | |
| Web Performance Optimizationdavila7/claude-code-templates | 33k | 7 repos | ~4k | Automated safety check: Pass | MIT |
Similar skills
- Official
Compare Array Bundle Size
PostHog/posthog-js
Quickly compare the posthog-js array.js bundle size in the current working tree against a git baseline using the repository's esbuild proxy.
Web Performance
mozilla/firefox-devtools-mcp
Find and fix why a website is slow by capturing and analyzing a Firefox performance profile, or by analyzing a profile the user already has (a saved file or a profiler.firefox.com share link).
Igniteui Wc Integrate With Framework
IgniteUI/igniteui-webcomponents
Install and integrate Ignite UI Web Components packages into React, Angular, Vue 3, LitElement, or vanilla JS/HTML apps, detecting the framework and applying framework-specific setup (package…
Web Performance Optimization
davila7/claude-code-templates
Optimize website and web application performance including loading speed, Core Web Vitals, bundle size, caching strategies, and runtime performance
npm Package Comparator
tinyfish-io/tinyfish-cookbook
Compare two or more npm packages side by side using live data — downloads, bundle size, GitHub stars, last update, known vulnerabilities, and community sentiment.
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Related
Works with
Categories
Questions about JS File Size
What does JS File Size do?
A skill your agent uses when auditing slow page loads, heavy assets, or rendering delays related to Optimize JavaScript bundle size. JS File Size is an agent skill from thedaviddias/Front-End-Checklist. Use when auditing slow page loads, heavy assets, or rendering delays related to Optimize JavaScript bundle size.
When should I use JS File Size?
JS File Size fits situations like: auditing slow page loads; rendering delays related to Optimize JavaScript bundle size.
How do I install JS File Size in Claude Code?
Run `npx skills add thedaviddias/Front-End-Checklist --skill js-file-size -a claude-code`. Or copy the skill folder (skills/js-file-size in thedaviddias/Front-End-Checklist) into .claude/skills/js-file-size in your project. Claude Code loads it when a task matches its description.
How do I install JS File Size in Codex?
Run `npx skills add thedaviddias/Front-End-Checklist --skill js-file-size -a codex`. Or copy the skill folder (skills/js-file-size in thedaviddias/Front-End-Checklist) into .agents/skills/js-file-size in your project. Codex loads it when a task matches its description.
Can I use JS File Size in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add thedaviddias/Front-End-Checklist --skill js-file-size -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/js-file-size, .gemini/skills/js-file-size, .github/skills/js-file-size and .opencode/skills/js-file-size in your project.
What does JS File Size need to run?
SKILL.md names no scripts, command-line tools or credentials: JS File Size is instructions for the agent only.
Does JS File Size access the network?
SKILL.md names 1 domain. As links in the text: frontendchecklist.io. This is read from the text; nothing was executed.
Is JS File Size safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does JS File Size use?
JS File Size is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does JS File Size use?
About 408 tokens (SKILL.md is roughly 1.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 592 tokens, read only when the agent opens those files.
What are the alternatives to JS File Size?
Skills that share tags, products or a category with JS File Size: I Optimize (boussadjra/vuestrata, 111 stars), Compare Array Bundle Size (PostHog/posthog-js, 634 stars), Web Performance (mozilla/firefox-devtools-mcp, 478 stars) and Igniteui Wc Integrate With Framework (IgniteUI/igniteui-webcomponents, 170 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains JS File Size?
thedaviddias (a GitHub user) maintains it in thedaviddias/Front-End-Checklist, which has 74,421 GitHub stars. The repository holds 390 skills in this directory. The repository was last updated on October 6, 2026.
Source: thedaviddias/Front-End-Checklist on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.