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Use when reviewing image assets, markup, and CDN or build transforms related to Use <picture> with an <img> fallback. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.
Passed 20 of 22 test cases with the skill, and 18 of 22 without it.
2 fixed18 passed either way2 still failing0 broke
Tokens, turns and time describe resource use, not a dollar price.
This benchmark measured an earlier version of the skill.
One of 2 test cases the skill fixed. Same model, same prompt, with and without the skill.
Can you explain how `<picture>` tag browser evaluation works alongside `<source>` elements and fallbacks? Also review our homepage template images and show where our markup fails to meet best practices.
| Checked | Without skill | With skill |
|---|---|---|
| The explanation states that a picture tag without an img child produces no output. | Missed | Passed |
| The review describes how to verify the markup fix using browser DevTools. | Missed | Passed |
The instructions your model reads when the skill loads.
A <picture> without an <img> fallback renders nothing in browsers that don't support <picture> (IE11) or don't support any of the <source> formats. The <img> child is also where alt, width, height, loading, and fetchpriority attributes live—these apply regardless of which source the browser selects.
<picture> must end with an <img> element—it is the required fallback and carries alt<source> elements are evaluated top-to-bottom; the first match winstype="image/avif" and type="image/webp" on <source> for format selection<img src> should point to a JPEG or PNG—the universal fallback for all browsersScan all elements in this codebase. Verify: 1) Every has an as its last child (required fallback). 2) The has an alt attribute. 3) The has width and height attributes. 4) elements appear before the child. 5) Each has either a srcset attribute or a media attribute. 6) format-selecting elements have a type attribute (type="image/avif", type="image/webp"). Flag any missing an child or with not as the last child.
For each element with issues: 1) If missing : add as the last child. 2) If is not last: move it to after all elements. 3) If elements lack type attributes for format selection: add type="image/avif" or type="image/webp". 4) Verify the points to a universally supported format (JPEG or PNG) as the ultimate fallback. Show the corrected markup.
Explain how the element works. Browsers evaluate elements in document order and use the first one whose conditions match (type, media, srcset). The element is the fallback for browsers that don't support (IE11) or don't support the source format. Without an child, is invalid HTML and produces no output. The alt attribute must be on the , not the elements—it applies regardless of which source is selected.
Review image assets, markup, and delivery configuration related to Use with an fallback. 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/rules/images/picture-element
test cases passed, vs 18 / 22 without
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