CLS Scanner - Sitemap & Layout Shift Tool
Audit image-related CLS issues, nested sitemap URLs, and export client-ready reports with PageSpeed Insights context.
Category
Developer Tools
Promo Text
Find image-related CLS problems fast, audit sitemap URLs in bulk, and export reports your team can actually use.
What CLS Scanner helps you do
CLS Scanner helps SEOs, developers, and agencies find image-related layout-shift risks faster while keeping the workflow practical for both single-page checks and bulk audit reviews.
Image-Focused CLS Audits
Check image dimensions, rendered sizing mismatches, and accessibility details that contribute to unstable layouts.
Agency-Friendly Reporting
Save audit history, compare runs, and export reports that are easier to share with clients or internal stakeholders.
How to Install
- 1Download the extension ZIP file from this page.
- 2Extract the ZIP to a folder on your computer.
- 3Open Chrome and go to chrome://extensions.
- 4Turn on Developer mode, click Load unpacked, and select the extracted extension folder.
The ZIP is meant to be extracted first. Chrome does not install a local ZIP directly from the downloads folder.
How to Use It
- 1Open the page you want to audit, then launch CLS Scanner from the Chrome toolbar or side panel.
- 2Run a single-page scan to review image dimensions, rendered sizing, and CLS-related warnings.
- 3Load a sitemap when you want to audit multiple URLs and compare results in bulk.
- 4Export findings as CSV, JSON, HTML, or a print-friendly report for clients or internal review.
Page Scanning
- Scan the active page from the popup or side panel
- Inspect image URLs, metadata, and rendered sizing
- Review HTML snippets tied to image-related CLS risks
Bulk Sitemap Audits
- Load nested sitemap trees
- Choose exactly which URLs to audit
- Review bulk results in a dedicated dashboard flow
Detailed Audit Insights
- Flag missing HTML width and height attributes
- Surface PSI CLS warnings alongside actual page risk
- Review alt quality, file format, file size, and sizing fit
Exports
- CSV for spreadsheet reviews
- JSON for automation and integrations
- HTML for shareable reports
- Print-friendly flow for PDF export
Who It Is For
- Technical SEO teams
- Web performance specialists
- Developers fixing Core Web Vitals issues
- Agencies preparing client-facing audit reports
Export Formats
CSV
JSON
HTML
PDF-Friendly
Privacy & Data Use
- Core scanning runs locally in the browser.
- Settings, history, and saved audit data stay in Chrome storage.
- Optional PSI reporting sends audited page URLs to Google PageSpeed Insights.
- Pro activation sends license data to Lemon Squeezy.
- Optional analytics can be enabled by the publisher through a proxy without audited page URLs or license keys.
Support & Next Steps
Need launch help, bug triage, or productization support for CLS Scanner? Use the support page for troubleshooting and license help, or reach out directly if you want help packaging the extension for a public release.
Interested in launching this extension?
We can help finalize the Chrome Web Store launch, polish the reporting workflow, and package the extension into a client-ready product experience.