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Agent skill

Srcset

by thedaviddias in thedaviddias/Front-End-Checklist

A skill your agent uses when reviewing image assets, markup, and CDN or build transforms related to Use srcset for responsive images.

MITAuto-check passed

Install Srcset

skills CLI
$ npx skills add thedaviddias/Front-End-Checklist --skill srcset -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install thedaviddias/Front-End-Checklist srcset --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/srcset .claude/skills/srcset && rm -rf skills-src

Use ~/.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/

Facts

Skill name
srcset
GitHub stars
74k
Token cost
~774 tokens
SKILL.md length
397 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 Use srcset for responsive images.

  • 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 Use srcset for responsive images

What it does

Srcset is an agent skill from thedaviddias/Front-End-Checklist. Use when reviewing image assets, markup, and CDN or build transforms related to Use srcset for responsive images. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.

Its SKILL.md is about 770 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 Use srcset for responsive images

Example prompts

  • “/srcset”

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

Srcset loads about 774 tokens when it runs, and up to ~2.2k if it reads all its reference files. Until then it costs about 52 tokens; SKILL.md has 397 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~52
When it runs · the whole SKILL.md, loaded when a task matches
~774
With references · SKILL.md plus every file in references/, read only if the agent opens them
~2.2k

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). 397 words, ~774 tokens.

Download SKILL.mdSave it as .claude/skills/srcset/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.
name
srcset
description
Use when reviewing image assets, markup, and CDN or build transforms related to Use srcset for responsive images. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.
metadata.category
images
metadata.priority
high
metadata.difficulty
intermediate
metadata.estimatedTime
15
metadata.source
frontendchecklist.io
metadata.url
https://frontendchecklist.io/rules/images/srcset

Use srcset for responsive images

Without srcset, every user—regardless of their device—downloads the same large image. A 1600px hero image served to a 375px mobile display downloads 4x the data needed. The srcset attribute lets browsers choose the optimal file automatically, reducing bandwidth by 50-80% for mobile users with no change to visual quality.

Quick Reference

  • Add srcset with width descriptors (400w, 800w) to all images wider than ~100px
  • Always pair srcset width descriptors with a sizes attribute—without sizes the browser assumes 100vw
  • Use density descriptors (1x, 2x) only for fixed-size images like avatars and icons
  • Keep src pointing to a fallback size for browsers that don't support srcset

Check

Scan all <img> elements in this codebase. Flag: 1) Any <img> wider than 100px (in CSS or layout) that lacks a srcset attribute. 2) Any <img> with srcset but missing a sizes attribute (necessary for width descriptors). 3) Any <img> using only density descriptors (1x, 2x) where width descriptors (400w, 800w) would be more appropriate. 4) Any srcset that provides only one size (no benefit over plain src). Report each finding with file path and line number.

Fix

For each <img> missing srcset: 1) Generate multiple width variants: typically 400w, 800w, 1200w (add 1600w for full-bleed images). 2) Add srcset listing each variant with its width descriptor. 3) Add a sizes attribute describing actual CSS layout width at each breakpoint. 4) Keep src pointing to a mid-range size (800w) as the fallback. 5) Add width and height attributes if missing. For each image, show the complete corrected HTML including srcset and sizes.

Show full SKILL.md (135 more words)Show less

Explain

Explain how srcset and the two descriptor types work. Width descriptors (400w, 800w) describe the intrinsic width of each candidate; the browser combines this with the sizes attribute to calculate which candidate provides the best pixel density for the current viewport. Density descriptors (1x, 2x) are simpler but less flexible—use them only for fixed-size images like avatars and icons. The sizes attribute is critical: without it, the browser assumes 100vw and always downloads the largest candidate even on narrow screens.

Code Review

Review image assets, markup, and delivery configuration related to Use srcset for responsive images. 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/srcset

© 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/srcset of thedaviddias/Front-End-Checklist.

  • SKILL.md
  • references/rule.md

Open the folder on GitHubat commit e8d14d0

Compare with similar skills

Srcset 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.

Srcset compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Srcset this skillthedaviddias/Front-End-Checklist74k—~774Automated safety check: PassMIT
Schema Markupalirezarezvani/claude-skills28k1 repos~2.9kAutomated safety check: PassMIT
Schema Markup Generatorsickn33/agentic-awesome-skills47k1 repos~2.1kAutomated safety check: PassMIT
Remotion Markupremotion-dev/remotion62k2 repos~4.5kAutomated safety check: PassCustom licence
Cdn Setupsickn33/agentic-awesome-skills47k2 repos~2.9kAutomated safety check: PassMIT
Schema Markupmohitagw15856/pm-claude-skills1.4k—~838Automated safety check: PassMIT

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Questions about Srcset

What does Srcset do?

A skill your agent uses when reviewing image assets, markup, and CDN or build transforms related to Use srcset for responsive images. Srcset is an agent skill from thedaviddias/Front-End-Checklist. Use when reviewing image assets, markup, and CDN or build transforms related to Use srcset for responsive images.

When should I use Srcset?

Srcset fits situations like: reviewing image assets; build transforms related to Use srcset for responsive images.

How do I install Srcset in Claude Code?

Run `npx skills add thedaviddias/Front-End-Checklist --skill srcset -a claude-code`. Or copy the skill folder (skills/srcset in thedaviddias/Front-End-Checklist) into .claude/skills/srcset in your project. Claude Code loads it when a task matches its description.

How do I install Srcset in Codex?

Run `npx skills add thedaviddias/Front-End-Checklist --skill srcset -a codex`. Or copy the skill folder (skills/srcset in thedaviddias/Front-End-Checklist) into .agents/skills/srcset in your project. Codex loads it when a task matches its description.

Can I use Srcset 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 srcset -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/srcset, .gemini/skills/srcset, .github/skills/srcset and .opencode/skills/srcset in your project.

What does Srcset need to run?

SKILL.md names no scripts, command-line tools or credentials: Srcset is instructions for the agent only.

Does Srcset 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 Srcset 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 Srcset use?

Srcset 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 Srcset use?

About 774 tokens (SKILL.md is roughly 3.1k 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 Srcset?

Skills that share tags, products or a category with Srcset: Schema Markup (alirezarezvani/claude-skills, 28k stars), Schema Markup Generator (sickn33/agentic-awesome-skills, 47k stars), Remotion Markup (remotion-dev/remotion, 62k stars) and Cdn Setup (sickn33/agentic-awesome-skills, 47k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Srcset?

thedaviddias (a GitHub user) maintains it in thedaviddias/Front-End-Checklist, which has 74,388 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.