React Doctor
makeplane/plane
Scans React code for lint, accessibility, bundle size and architecture issues, reports a health score and checks that changes do not lower it.
A skill your agent uses when auditing the image pipeline, static assets in public/, CMS-managed media, or image CDN transforms.
Install Image File Size
$ npx skills add thedaviddias/Front-End-Checklist --skill image-file-size -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install thedaviddias/Front-End-Checklist image-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/image-file-size .claude/skills/image-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 "image-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/image-file-size into .claude/skills/image-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "image-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/image-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 image-file-size -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install thedaviddias/Front-End-Checklist image-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/image-file-size .agents/skills/image-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 "image-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/image-file-size into .agents/skills/image-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "image-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 image-file-size -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install thedaviddias/Front-End-Checklist image-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/image-file-size .cursor/skills/image-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 "image-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/image-file-size into .cursor/skills/image-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "image-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/image-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 image-file-size -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install thedaviddias/Front-End-Checklist image-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/image-file-size .gemini/skills/image-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 "image-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/image-file-size into .gemini/skills/image-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "image-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 image-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 image-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/image-file-size .github/skills/image-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 "image-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/image-file-size into .github/skills/image-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "image-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 image-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 image-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/image-file-size .opencode/skills/image-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 "image-file-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/image-file-size into .opencode/skills/image-file-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "image-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
image-file-size- GitHub stars
- 74k
- Token cost
- ~792 tokens
- SKILL.md length
- 386 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 the image pipeline, static assets in public/, CMS-managed media, or image CDN transforms.
- Auditing the image pipeline
- 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
- Static assets in public/
What it does
Image File Size is an agent skill from thedaviddias/Front-End-Checklist. Use when auditing the image pipeline, static assets in public/, CMS-managed media, or image CDN transforms. Separate file-size problems from dimension mismatches so you can tell whether the issue is compression, format choice, or responsive delivery.
Its SKILL.md is about 790 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. 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 the image pipeline
- Static assets in public/
- CMS-managed media
- Image CDN transforms
Example prompts
- “/image-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
Image File Size loads about 792 tokens when it runs, and up to ~2.1k if it reads all its reference files. Until then it costs about 67 tokens; SKILL.md has 386 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). 386 words, ~792 tokens.
Download SKILL.mdSave it as
.claude/skills/image-file-size/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- image-file-size
- description
- Use when auditing the image pipeline, static assets in `public/`, CMS-managed media, or image CDN transforms. Separate file-size problems from dimension mismatches so you can tell whether the issue is compression, format choice, or responsive delivery.
- metadata.category
- images
- metadata.priority
- high
- metadata.difficulty
- intermediate
- metadata.estimatedTime
- 20
- metadata.source
- frontendchecklist.io
- metadata.url
- https://frontendchecklist.io/rules/images/image-file-size
Keep image file sizes within recommended limits
Images account for over 50% of average page weight according to HTTP Archive data. Oversized images waste user bandwidth (costly on mobile data plans), delay Largest Contentful Paint (LCP), and increase bounce rates. A 1-second delay in mobile page load can reduce conversions by up to 20% according to Google research.
Quick Reference
- Photos: target under 200KB (WebP 80% quality); under 400KB for full-bleed hero images
- Graphics/icons: target under 50KB; use SVG for vector graphics
- WebP is typically 25-35% smaller than equivalent-quality JPEG (per web.dev)
- AVIF is typically 40-50% smaller than equivalent-quality JPEG (per web.dev)
Check
Audit all image assets in this project. For each image: 1) Check the file size in bytes. 2) Flag any photo (JPEG/WebP/AVIF) over 200KB. 3) Flag any graphic/icon (PNG/SVG) over 100KB. 4) Flag any hero or full-width image over 400KB. 5) Flag any thumbnail (under 200px wide) over 30KB. Also check if Lighthouse reports 'Properly size images' or 'Efficiently encode images' as opportunities. Report each oversized image with its path, current size, and an estimated target size.
Fix
For each oversized image: 1) Convert JPEG/PNG to WebP at 80% quality using Squoosh, Sharp, or ImageOptim—this typically yields 25-35% size reduction over optimised JPEG. 2) Try AVIF at 60% quality for further reduction (often 40-50% smaller than JPEG). 3) Strip metadata (EXIF/IPTC) from images served on the web. 4) For PNGs, run through oxipng or pngquant for lossless or near-lossless compression. 5) For SVGs, run through SVGO. 6) Implement multiple srcset sizes so mobile users download smaller files.
Show full SKILL.md (126 more words)Show less
Explain
Explain how oversized images impact web performance. Images are typically the largest assets on a page—HTTP Archive data consistently shows images account for 40-60% of total page weight. Each KB saved reduces transfer time, especially on mobile networks (4G averages 20Mbps, with significant latency). Large images also delay Largest Contentful Paint (LCP), the primary Core Web Vitals metric. Google's Lighthouse flags images that could be reduced by more than 4KB as an opportunity.
Code Review
Inspect image assets, build transforms, CMS output, and rendered markup. Flag photos above the documented file-size thresholds, hero images that exceed budget without justification, and image pipelines that ship original uploads instead of compressed responsive variants.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/images/image-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/image-file-size of thedaviddias/Front-End-Checklist.
- SKILL.md
- references/rule.md
Open the folder on GitHubat commit e8d14d0
Compare with similar skills
Image 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 |
|---|---|---|---|---|---|---|
| Image File Size this skillthedaviddias/Front-End-Checklist | 74k | — | ~792 | Automated safety check: Pass | MIT | |
| React Doctormakeplane/plane | 61k | 12 repos | ~657 | Automated safety check: Pass | AGPL-3.0 | |
| Fixing Motion Performanceibelick/ui-skills | 9.6k | 5 repos | ~1.4k | Automated safety check: Pass | MIT | |
| GSAP Performance Tuninggreensock/gsap-skills | 16k | 3 repos | ~1k | Automated safety check: Pass | MIT | |
| React Frontend Development Guidelinesdiet103/claude-code-infrastructure-showcase | 10k | 2 repos | ~2.9k | Automated safety check: Pass | MIT | |
| Web Quality Auditaddyosmani/web-quality-skills | 2.9k | — | ~2.6k | Automated safety check: Pass | MIT |
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Guides the agent to keep GSAP animations smooth by animating transforms and opacity, batching DOM reads and writes, and avoiding layout-heavy properties.
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Google SEO APIs: Search Console (Search Analytics, URL Inspection, Sitemaps), PageSpeed Insights v5, CrUX field data with 25-week history, Indexing API v3, and GA4 organic traffic.
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Related
Categories
Questions about Image File Size
What does Image File Size do?
A skill your agent uses when auditing the image pipeline, static assets in public/, CMS-managed media, or image CDN transforms. Image File Size is an agent skill from thedaviddias/Front-End-Checklist. Use when auditing the image pipeline, static assets in public/, CMS-managed media, or image CDN transforms.
When should I use Image File Size?
Image File Size fits situations like: auditing the image pipeline; static assets in public/; CMS-managed media; image CDN transforms.
How do I install Image File Size in Claude Code?
Run `npx skills add thedaviddias/Front-End-Checklist --skill image-file-size -a claude-code`. Or copy the skill folder (skills/image-file-size in thedaviddias/Front-End-Checklist) into .claude/skills/image-file-size in your project. Claude Code loads it when a task matches its description.
How do I install Image File Size in Codex?
Run `npx skills add thedaviddias/Front-End-Checklist --skill image-file-size -a codex`. Or copy the skill folder (skills/image-file-size in thedaviddias/Front-End-Checklist) into .agents/skills/image-file-size in your project. Codex loads it when a task matches its description.
Can I use Image 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 image-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/image-file-size, .gemini/skills/image-file-size, .github/skills/image-file-size and .opencode/skills/image-file-size in your project.
What does Image File Size need to run?
SKILL.md names no scripts, command-line tools or credentials: Image File Size is instructions for the agent only.
Does Image 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 Image 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 Image File Size use?
Image 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 Image File Size use?
About 792 tokens (SKILL.md is roughly 3.2k 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 1.3k tokens, read only when the agent opens those files.
What are the alternatives to Image File Size?
Skills that share tags, products or a category with Image File Size: React Doctor (makeplane/plane, 61k stars), Fixing Motion Performance (ibelick/ui-skills, 9.6k stars), GSAP Performance Tuning (greensock/gsap-skills, 16k stars) and React Frontend Development Guidelines (diet103/claude-code-infrastructure-showcase, 10k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Image 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.