30x-seo-images

30x-seo-images is a skill for Claude Code from norahe0304-art/30x-seo. It costs 58 tokens per session (1,409 once invoked), scanned A, a copy of seo-images, MIT.

An image audit for search visibility, page speed, and layout stability. It checks image descriptions, file sizes, formats, responsive behavior, lazy loading, and whether images shift the page while loading.

In plain words
What is it for?
Use it to review image alt text, compression targets, WebP or AVIF usage, responsive images, lazy loading, and safeguards against cumulative layout shift.
Why use it?
It helps reduce accessibility and SEO problems, large downloads, slow pages, and unexpected layout movement caused by images.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: mentions CLAUDE.md.

Good fit Use it to review image alt text, compression targets, WebP or AVIF usage, responsive images, lazy loading, and safeguards against cumulative layout shift.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/norahe0304-art/30x-seo/30x-seo-images
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add norahe0304-art/30x-seo --skill 30x-seo-images
Clone the repo
git clone --depth 1 https://github.com/norahe0304-art/30x-seo

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for 30x-seo-images

README.md
[![agentmods](https://agentmods.dev/badge/skills/norahe0304-art/30x-seo/30x-seo-images/github.svg)](https://agentmods.dev/skills/norahe0304-art/30x-seo/30x-seo-images)
Your own site
<a href="https://agentmods.dev/skills/norahe0304-art/30x-seo/30x-seo-images"><img src="https://agentmods.dev/badge/skills/norahe0304-art/30x-seo/30x-seo-images/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for 30x-seo-images

Your own site · 80×15
<a href="https://agentmods.dev/skills/norahe0304-art/30x-seo/30x-seo-images"><img src="https://agentmods.dev/badge/skills/norahe0304-art/30x-seo/30x-seo-images.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 58 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,409 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 78% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00058 $0.01409
Opus 5 $0.00029 $0.00705
Sonnet 5 $0.00012 $0.00282
Haiku 4.5 $0.00006 $0.00141

Measured 12d ago against content hash d47a1a5bf19b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

30x-seo-images scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

78% identical to seo-images — 22 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/30x-seo-images/SKILL.md · 174 lines

How it starts

The opening of the file, as written. The whole thing — 174 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Image Optimization Analysis

Checks

Alt Text

  • Present on all <img> elements (except decorative: role="presentation")
  • Descriptive: describes the image content, not "image.jpg" or "photo"
  • Includes relevant keywords where natural, not keyword-stuffed
  • Length: 10-125 characters

Good examples:

  • "Professional plumber repairing kitchen sink faucet"
  • "Red 2024 Toyota Camry sedan front view"
  • "Team meeting in modern office conference room"

Bad examples:

  • "image.jpg" (filename, not description)
  • "plumber plumbing plumber services" (keyword stuffing)
  • "Click here" (not descriptive)

File Size

Tiered thresholds by image category:

Image Category Target Warning Critical
Thumbnails < 50KB > 100KB > 200KB
Content images < 100KB > 200KB > 500KB
Hero/banner images < 200KB > 300KB > 700KB

Recommend compression to target thresholds where possible without quality loss.

Format

Format Browser Support Use Case
WebP 97%+ Default recommendation
AVIF 92%+ Best compression, newer
JPEG 100% Fallback for photos
PNG 100% Graphics with transparency
SVG 100% Icons, logos, illustrations

Recommend WebP/AVIF over JPEG/PNG. Check for <picture> element with format fallbacks.

Recommended <picture> Element Pattern

Use progressive enhancement with the most efficient format first:

<picture>
  <source srcset="image.avif" type="image/avif">
  <source srcset="image.webp" type="image/webp">
  <img src="image.jpg" alt="Descriptive alt text" width="800" height="600" loading="lazy" decoding="async">
</picture>

The browser will use the first supported format. Current browser support: AVIF 93.8%, WebP 95.3%.

JPEG XL — Emerging Format

In November 2025, Google's Chromium team reversed its 2022 decision and announced it will restore JPEG XL support in Chrome using a Rust-based decoder. The implementation is feature-complete but not yet in Chrome stable. JPEG XL offers lossless JPEG recompression (~20% savings with zero quality loss) and competitive lossy compression. Not yet practical for web deployment, but worth monitoring for future adoption.

Read the full file on GitHub · 174 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 12d ago First seen · 174 lines · 58 tokens per session scan A d47a1a5bf19b

Subscribe to this mod's changes

30x-seo-images is a skill published in the GitHub repository norahe0304-art/30x-seo (51 stars, last pushed 6mo ago), licensed MIT. It adds 58 tokens to every session and 1,409 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 78% identical to seo-images, differing in 22 lines, and is treated as a copy.

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