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Performance fix guide

No Modern Image Formats (WebP/AVIF)

All images use legacy formats (JPEG/PNG/GIF). Modern formats like WebP and AVIF provide 25-50% smaller file sizes with equivalent quality.

Issue ID: PERF-IMG-FORMAT-001
Severity: medium
Impact: Med
Effort: M

Use this article when

  • You need deeper remediation guidance than the issue card can show.
  • You want CMS-specific steps before handing the fix to a developer.
  • You want a repeatable re-check path after shipping the change.
Re-run full audit

What this issue is

All images use legacy formats (JPEG/PNG/GIF). Modern formats like WebP and AVIF provide 25-50% smaller file sizes with equivalent quality.

Why it matters

All images use legacy formats (JPEG/PNG/GIF). Modern formats like WebP and AVIF provide 25-50% smaller file sizes with equivalent quality. This affects load speed, Core Web Vitals, and how many visitors stay long enough to convert.

How we detect it

  • FreeSiteAudit flags this issue when the rule for PERF-IMG-FORMAT-001 fails and the page evidence points to Dom body.
  • You can usually confirm this by checking the page source or the relevant page settings inside your CMS.

Evidence examples

Check the affected page source, rendered output, or relevant CMS setting to confirm the missing or incorrect element.

How to fix it

  1. 1Convert images to WebP format (supported by all modern browsers)
  2. 2Use AVIF for even better compression where browser support allows
  3. 3Use <picture> element with WebP/AVIF source and JPEG/PNG fallback
  4. 4Many CDNs offer automatic image format conversion

How to re-check it

  • Check that images are served in WebP or AVIF format using browser DevTools Network tab

Related tools

This issue is best verified with the full FreeSiteAudit crawl rather than a single-point mini tool.