Responsive Design
wshobson/agents
Implement modern responsive layouts using container queries, fluid typography, CSS Grid, and mobile-first breakpoint strategies.
A skill your agent uses when reviewing image assets, markup, and CDN or build transforms related to Serve images at the correct display size.
MITAuto-check passed
Install Responsive Size
$ npx skills add thedaviddias/Front-End-Checklist --skill responsive-size -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install thedaviddias/Front-End-Checklist responsive-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/responsive-size .claude/skills/responsive-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 "responsive-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/responsive-size into .claude/skills/responsive-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "responsive-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/responsive-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 responsive-size -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install thedaviddias/Front-End-Checklist responsive-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/responsive-size .agents/skills/responsive-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 "responsive-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/responsive-size into .agents/skills/responsive-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "responsive-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 responsive-size -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install thedaviddias/Front-End-Checklist responsive-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/responsive-size .cursor/skills/responsive-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 "responsive-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/responsive-size into .cursor/skills/responsive-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "responsive-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/responsive-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 responsive-size -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install thedaviddias/Front-End-Checklist responsive-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/responsive-size .gemini/skills/responsive-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 "responsive-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/responsive-size into .gemini/skills/responsive-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "responsive-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 responsive-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 responsive-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/responsive-size .github/skills/responsive-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 "responsive-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/responsive-size into .github/skills/responsive-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "responsive-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 responsive-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 responsive-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/responsive-size .opencode/skills/responsive-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 "responsive-size" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/responsive-size into .opencode/skills/responsive-size/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "responsive-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
responsive-size- GitHub stars
- 74k
- Token cost
- ~805 tokens
- SKILL.md length
- 406 words
- Files
- 2 (incl. references)
- Skills in repo
- 390
- Repo updated
- First seen
- Licence
- MIT
At a glance
A skill your agent uses when reviewing image assets, markup, and CDN or build transforms related to Serve images at the correct display size.
- Reviewing image assets
- 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
- Build transforms related to Serve images at the correct display size
What it does
Responsive Size is an agent skill from thedaviddias/Front-End-Checklist. Use when reviewing image assets, markup, and CDN or build transforms related to Serve images at the correct display size. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.
Its SKILL.md is about 810 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`).
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
- Reviewing image assets
- Build transforms related to Serve images at the correct display size
Example prompts
- “/responsive-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
Responsive Size loads about 805 tokens when it runs, and up to ~2.2k if it reads all its reference files. Until then it costs about 57 tokens; SKILL.md has 406 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). 406 words, ~805 tokens.
Download SKILL.mdSave it as
.claude/skills/responsive-size/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- responsive-size
- description
- Use when reviewing image assets, markup, and CDN or build transforms related to Serve images at the correct display size. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.
- metadata.category
- images
- metadata.priority
- high
- metadata.difficulty
- intermediate
- metadata.estimatedTime
- 20
- metadata.source
- frontendchecklist.io
- metadata.url
- https://frontendchecklist.io/rules/images/responsive-size
Serve images at the correct display size
A single oversized hero image can add several megabytes to a page load unnecessarily. On mobile devices with 375px screens, serving a 1600px image downloads 4x the data users need. The 'Properly size images' Lighthouse audit consistently identifies this as one of the highest-impact performance opportunities on most websites.
Quick Reference
- Serving a 1600px image in a 400px container wastes ~16x the necessary bandwidth
- Use
srcsetwith width descriptors andsizeswith actual layout widths - The
sizesattribute is critical—without it the browser assumes100vwand picks the largest image - Lighthouse 'Properly size images' audit reports estimated savings per oversized image
Check
Audit images in this codebase for oversizing. Use Lighthouse 'Properly size images' audit results as the primary signal. For each <img> in the HTML: 1) Compare the image file's intrinsic width to the element's rendered CSS width (check CSS rules, container constraints). 2) Flag any image where the intrinsic width is more than 2x the rendered width at any common viewport size. 3) Check for srcset usage—images over 200px wide should have srcset variants. 4) Check sizes attribute accuracy—does it reflect the actual CSS layout?
Fix
For each oversized image: 1) Generate multiple size variants: 400w, 800w, 1200w, 1600w (use Sharp or Squoosh). 2) Add srcset listing each variant with its width descriptor. 3) Add a sizes attribute describing the image's display width at each breakpoint (e.g., sizes="(max-width: 600px) 100vw, (max-width: 1200px) 50vw, 400px"). 4) For art direction (different crops), use <picture> with media attributes. 5) For the <img> src fallback, use the medium size (800w). Show complete before/after HTML.
Show full SKILL.md (137 more words)Show less
Explain
Explain why serving oversized images wastes bandwidth. If a browser renders an image at 400px wide but the image file is 2000px wide, the browser downloads ~25x more pixel data than it can display (bandwidth scales with pixel count, not linear dimensions). The Lighthouse 'Properly size images' audit estimates potential savings in KiB for each oversized image. The sizes attribute is the key to accuracy—without it, the browser assumes 100vw and downloads the largest srcset candidate even on narrow viewports.
Code Review
Review image assets, markup, and delivery configuration related to Serve images at the correct display size. Flag exact files or components where format choice, sizing, or loading behavior violates the rule, and describe how to confirm the fix in DevTools.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/images/responsive-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/responsive-size of thedaviddias/Front-End-Checklist.
- SKILL.md
- references/rule.md
Open the folder on GitHubat commit e8d14d0
Compare with similar skills
Responsive 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 |
|---|---|---|---|---|---|---|
| Responsive Size this skillthedaviddias/Front-End-Checklist | 74k | — | ~805 | Automated safety check: Pass | MIT | |
| Responsive Designwshobson/agents | 40k | 2 repos | ~498 | Automated safety check: Pass | MIT | |
| Schema Markupalirezarezvani/claude-skills | 28k | 1 repos | ~2.9k | Automated safety check: Pass | MIT | |
| Market Sizingphuryn/pm-skills | 27k | — | ~1.1k | Automated safety check: Pass | MIT | |
| Performing Ransomware Responsemukul975/Anthropic-Cybersecurity-Skills | 34k | — | ~2.9k | Automated safety check: Pass | Apache-2.0 | |
| Incident Responsesickn33/agentic-awesome-skills | 47k | 1 repos | ~3.7k | Automated safety check: Pass | MIT |
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Questions about Responsive Size
What does Responsive Size do?
A skill your agent uses when reviewing image assets, markup, and CDN or build transforms related to Serve images at the correct display size. Responsive Size is an agent skill from thedaviddias/Front-End-Checklist. Use when reviewing image assets, markup, and CDN or build transforms related to Serve images at the correct display size.
When should I use Responsive Size?
Responsive Size fits situations like: reviewing image assets; build transforms related to Serve images at the correct display size.
How do I install Responsive Size in Claude Code?
Run `npx skills add thedaviddias/Front-End-Checklist --skill responsive-size -a claude-code`. Or copy the skill folder (skills/responsive-size in thedaviddias/Front-End-Checklist) into .claude/skills/responsive-size in your project. Claude Code loads it when a task matches its description.
How do I install Responsive Size in Codex?
Run `npx skills add thedaviddias/Front-End-Checklist --skill responsive-size -a codex`. Or copy the skill folder (skills/responsive-size in thedaviddias/Front-End-Checklist) into .agents/skills/responsive-size in your project. Codex loads it when a task matches its description.
Can I use Responsive 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 responsive-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/responsive-size, .gemini/skills/responsive-size, .github/skills/responsive-size and .opencode/skills/responsive-size in your project.
What does Responsive Size need to run?
SKILL.md names no scripts, command-line tools or credentials: Responsive Size is instructions for the agent only.
Does Responsive 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 Responsive 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 Responsive Size use?
Responsive 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 Responsive Size use?
About 805 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 1.4k tokens, read only when the agent opens those files.
What are the alternatives to Responsive Size?
Skills that share tags, products or a category with Responsive Size: Responsive Design (wshobson/agents, 40k stars), Schema Markup (alirezarezvani/claude-skills, 28k stars), Market Sizing (phuryn/pm-skills, 27k stars) and Performing Ransomware Response (mukul975/Anthropic-Cybersecurity-Skills, 34k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Responsive Size?
thedaviddias (a GitHub user) maintains it in thedaviddias/Front-End-Checklist, which has 74,412 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.