Audit rules
Images in Legacy Formats
Images whose URL extension is jpg, jpeg, png, gif, bmp, tif or tiff. The format is read from the extension of the src URL; webp, avif, svg and unknown extensions (data: URIs included) pass. In a QuikSEO audit, a failure has info severity and counts against the score. The exact condition, its exceptions and its sources follow below.
images.legacy_formatsInfo01 — Definition
How This Rule Is Checked
The rule is a pure function of the fetched page: no extra requests, no account settings. The same input always gives the same result.
Rule Severity and Score
- Rule id
images.legacy_formats- Group
- Images
- Severity of a failure
- Info
- Counts in the score
- Yes, whenever it applies to the page
- Required for a score
- No
- Replaces the check
image_formats
Condition and Exceptions
- Condition
- Images whose URL extension is jpg, jpeg, png, gif, bmp, tif, tiff → fail (info) with count; webp, avif, svg and unknown extensions pass
- Exceptions
- No images → not_applicable; an <img> that is the fallback of a <picture> offering a WebP or AVIF <source> (by type or extension) is not counted
Sources and Project Decision
- Sources
- Serve images in modern formats | Lighthouse | Chrome for Developers (Chrome for Developers, Q21)
- Project decision
- An <img> that is the fallback of a <picture> offering a WebP or AVIF <source> is not flagged.
02 — Images
Other Rules in This Group
The other checks of the same group, each with its own condition and sources.
- Image Alt Attribute Missingimages.alt_missing
- Image Lazy Loadingimages.lazy_loading
- Image Dimensions Missingimages.missing_dimensions