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Use when reviewing image assets, markup, and CDN or build transforms related to Use AVIF format for modern browsers. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.
Use when reviewing templates, rendered HTML, or shared components related to Implement accessible breadcrumb navigation. Validate the final browser-facing markup, not just the source framework abstraction.
Use when auditing metadata, crawlability, structured data, or indexability related to Implement valid BreadcrumbList schema. Verify the rendered HTML and HTTP response rather than relying only on source files.
Use when reviewing templates, rendered HTML, or shared components related to Declare UTF-8 character encoding. Validate the final browser-facing markup, not just the source framework abstraction.
Use when reviewing templates, rendered HTML, or shared components related to Set text direction for RTL languages. Validate the final browser-facing markup, not just the source framework abstraction.
Use when auditing a site's meta tag uniqueness, generating page-specific meta descriptions, or reviewing CMS templates that inject the same description globally.
Use when you need to find the 2-3 most popular and well-maintained npm packages relevant to a frontend checklist rule, validate they meet quality thresholds, and add them to the rule's frontmatter.
| name | avif-format |
| description | Use when reviewing image assets, markup, and CDN or build transforms related to Use AVIF format for modern browsers. Check encoded size, rendered size, loading strategy, and above-the-fold impact together. |
| metadata | {"category":"images","priority":"medium","difficulty":"intermediate","estimatedTime":"20","source":"frontendchecklist.io","url":"https://frontendchecklist.io/en/rules/images/avif-format"} |
AVIF provides the best compression available—50% smaller than JPEG and 20% smaller than WebP—dramatically reducing bandwidth and improving load times.
Check if the website supports AVIF format for even better compression than WebP.
Implement AVIF support with proper fallbacks for browsers that don't support it.
Explain how AVIF provides 50% better compression than JPEG with superior quality.
Review image assets, markup, and delivery configuration related to Use AVIF format for modern browsers. Flag exact files or components where format choice, sizing, or loading behavior violates the rule, and describe how to confirm the fix in DevTools.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/images/avif-format
