img.unsupported-format

What to change

A finding of this rule on a page carries the exact edits for that page: the markup it quotes, and what to write instead.

When it runs

Runs on every SEO audit: of a page, a crawl, a build directory or HTML. Info is a best practice: worth doing, rarely urgent, and --no-info leaves it out. Each finding takes 1 point off the page's score.

The severity here is the rule's usual one: a finding can be raised or lowered when the page gives a reason.

Run it, or skip it

Check a page for this rule alone, after a fix for instance:

npx @rivi-software/agentic-seo-check audit https://example.com --rule img.unsupported-format

Or from an assistant, with the MCP tool seo_audit_page:

{
  "url": "https://example.com",
  "rules": [
    "img.unsupported-format"
  ]
}

To leave it out of an audit, pass --disable img.unsupported-format on the command, or disableRules: ["img.unsupported-format"] to a tool.

• Warningimg.alt-missingImages without an alt attribute.
• Infoimg.alt-filenameImage alt text looks like a filename (IMG_1234.jpg, screenshot.png).
• Infoimg.dimensions-missingImages without explicit width and height attributes, which causes layout shift (CLS) while they load.
• Infoimg.src-missingImages without a src attribute (usually lazy-loading via data-src without a fallback).
• Infoimg.lazy-above-foldThe first large image on the page, likely in the first screen and often the Largest Contentful Paint, has loading="lazy", which delays it (info). An image with both fetchpriority="high" and loading="lazy" contradicts itself (warning).
• Infoimg.srcset-missingImages 640 pixels wide or more (by their width attribute) have no srcset or <picture>, so phones download the full-size file.