AltCatch: Alt Text and Broken Image Checker
Inspect a page for missing alt text and broken images with the AltCatch Chrome extension. Review each finding and export a Markdown report.
AltCatch
example.com/about
- Missing altNo alt attribute
<img src="hero-photo.jpg"> - Broken imageHEAD 404
<img src="/logo-old.png" alt="Company logo"> - Placeholder altLazy filler text
<img alt="image" src="banner.png"> - DecorativeIntentional empty alt
<img alt="" src="divider.svg">
What AltCatch catches
Five severity classes help prioritize review. Check each finding in context; an automated flag alone does not determine WCAG conformance. Decorative entries are shown for context.
Missing alt
CriticalImages without alt attributes. Review text alternatives against WCAG 1.1.1.
Broken images
Critical404s and load failures, verified with lightweight HEAD requests.
Placeholder alt
WarningLazy alt text like "image", "untitled", or the raw filename.
Whitespace-only alt
WarningAlt attributes that contain only spaces. Screen readers skip them.
Decorative alt=""
InfoIntentionally empty alt for decorative images. Shown collapsed, for context.
How it works
On-demand. Page-by-page. Everything runs locally in your browser.
- 1
Click the AltCatch icon or open the side panel on any page.
- 2
AltCatch scans every <img> in the DOM and resolves its real source.
- 3
Broken images are verified asynchronously — no heavy downloads of the actual files.
- 4
Results stream into a grouped checklist with a live health breakdown.
- 5
Export to Markdown or copy to clipboard. Done.
How to use AltCatch on your page
- Install AltCatch from the Chrome Web Store, then open any normal https:// page and click the AltCatch icon (or open its side panel) to scan every <img> in that page's DOM.
- Read the grouped checklist — missing alt and broken images surface as critical findings, while placeholder text like "image" or whitespace-only alt is flagged as a warning.
- Fix each flagged image by writing meaningful alt text that conveys its purpose, per the WCAG 2.2 non-text content guidance (W3C Understanding 1.1.1) and the MDN alt attribute reference; leave genuinely decorative images with an empty alt="".
- Re-run the audit after fixing and compare against your saved history in the side panel to review whether the reported issues are resolved.
- Export the final report as Markdown for a PR description, ticket, or accessibility review.
Built for
Anyone who has to ship pages that pass an accessibility review or rank in image search.
Web developers
shipping accessible HTML
SEO specialists
auditing image SEO and image search visibility
Accessibility auditors
documenting WCAG 2.2 compliance
QA testers
writing reproducible bug tickets
Why AltCatch
Other tools spot the same images. AltCatch turns them into a deliverable.
Markdown export
Markdown export drops straight into GitHub, Linear, Notion, or PR descriptions — no reformatting.
Five-tier severity classification
Severity classification beyond "missing alt" — catches lazy, placeholder, and decorative cases other tools miss.
Audit history
Audit history so you can track progress across pages and re-check after a fix.
Zero signup, zero servers
No account, no signup, no upload. Open it and audit.
AltCatch runs 100% locally. No data ever leaves your browser.
What's next
AltCatch ships today with on-demand, page-by-page auditing — the foundation for full-site, sitemap-driven auditing in a future release. Every audit you run now carries forward into your history.
Ship accessible images. Today.
Install AltCatch, audit a page, export the report, and ship the fix.
Related Accessibility & Image SEO Tools
Audit WCAG 2.2 AA/AAA contrast ratios
Meta & OG PreviewerLive Google, X, Facebook, LinkedIn previews
Open Graph GeneratorGenerate social-share meta tags
Image to Base64Inline images as data: URLs
Favicon GeneratorBuild a complete favicon set
Image CompressorShrink image weight before audit
HTML FormatterClean up semantic markup
CSS SpecificityDebug selector overrides
Frequently asked questions
Why does AltCatch not appear on some pages?
Chrome blocks all extensions on chrome:// URLs, the Chrome Web Store itself, and some PDF viewers, so the side panel cannot audit there. Try a supported https:// page and check the extension permissions.
What do the five severity tiers mean?
Missing alt text flags a potential WCAG 1.1.1 non-text-content issue; review the image purpose and any equivalent accessible name. Broken images need review but do not automatically establish a WCAG failure. Placeholder and whitespace-only alternatives are warnings; decorative images with empty alt text are listed for context.
How are broken images verified without slowing the audit?
Each image's resolved URL receives a lightweight HEAD request that checks status only — the browser never downloads the actual image files. Results stream into the grouped checklist as they resolve instead of waiting for the whole page.
Where is my audit history stored?
In chrome.storage.local on your device only — nothing is cloud-synced. Clearing Chrome's site data, uninstalling the extension, or using a fresh profile wipes it, so re-run an audit if you switch machines.
Does auditing a page send its data anywhere?
DOM analysis and reports stay local. Broken-image checks send HEAD requests directly to image hosts, which receive ordinary request data. Audit results are not sent to Toolk. The Toolk website uses page analytics separately from the extension.
Can I audit an entire site at once?
AltCatch audits the current page on demand. For broader coverage, inspect representative page templates individually and use the Markdown reports to track findings. The current workflow is not a sitemap crawler.
Last updated: September 15, 2026 · Runs 100% in your browser — no uploads, tool input is not sent to Toolk.