Image SEO Audit Claude Skill
This skill audits a website's images for SEO and Core Web Vitals compliance and produces an actionable report. It crawls pages to find missing or empty alt text, absent width and height attributes, missing lazy-loading, oversized files and legacy formats, generic filenames, and broken image URLs, then recommends concrete fixes for each one.
Quick Take
Point the skill at a site URL, sitemap, file list, or local HTML folder. It builds an image inventory with src, alt, dimensions, and loading attributes, optionally fetches files to check byte size and status, then returns a severity-ranked report with fixes like descriptive alt text and WebP conversion.
What The Skill Checks
- High-severity failures: images with no
altattribute, which removes the primary accessibility signal and the main way search engines understand image content, and broken images returning a non-200 status when file checking is enabled. - Medium-severity performance issues: missing
width/heightattributes that cause Cumulative Layout Shift, a Core Web Vitals ranking factor, and oversized files above the 200 KB default budget that slow Largest Contentful Paint. - Low-severity and informational signals: below-fold images missing
loading="lazy", legacy JPEG/PNG/GIF formats with no WebP or AVIF source, generic filenames likeIMG_1234, alt text over 125 characters or with redundant "image of" prefixes, plus decorative empty alt, duplicate alt text, and CSS background images the crawler cannot see.
How The Skill Is Packaged
The skill follows the standard Claude Agent Skill structure: a SKILL.md file with YAML frontmatter and workflow instructions, a references/ folder with the full audit check definitions and report template, and a scripts/ folder with Python scripts that extract every image from pages and audit the resulting inventory. Copy the skill folder into your Claude skills directory and Claude invokes it automatically when a request matches its description.
Skill Files
Every file in the skill is embedded below directly from the Claude-SEO-Skills repository, so you can review exactly what the skill instructs Claude to do before installing it.
SKILL.md
The skill definition: frontmatter, inputs to collect (including whether to fetch images for byte-size validation), the audit workflow, and the resources the skill relies on.
Audit Checks Reference (references/audit-checks.md)
Full definitions, thresholds, and rationale for every audit check, from missing alt text and broken images to oversized files, legacy formats, and redundant alt prefixes.
Report Template (references/report-template.md)
The output structure the skill follows when writing the final audit report, including summary statistics and prioritized fixes.
Image Extractor Script (scripts/extract_images.py)
Crawls a live site, file list, or local HTML folder within the configured page limits and collects every image with its src, alt, dimensions, loading attribute, and file size when --check-files is used.
Image Auditor Script (scripts/audit_images.py)
Runs the audit checks against the image inventory, applying the oversized-file byte threshold and severity classifications, and outputs the structured audit report data.