Images: Incorrectly Sized Images

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Incorrectly Sized Images

Images identified where their real dimensions (WxH) do not match the display dimensions when rendered.

If there is an estimated 4kb file size difference or more, the image is flagged for potential optimisation.

In particular, this can help identify oversized images, which can contribute to poor page load speed. It can also help identify smaller sized images, that are being stretched when rendered.

How to Analyse in the SEO Spider

View URLs with this issue in the ‘Images’ tab and ‘Incorrectly Sized Images’ filter, and export all URLs using the ‘Export’ button.

Enable JavaScript rendering mode via ‘Config > Spider > Rendering’ and select ‘JavaScript’ and run crawl analysis via ‘Crawl Analysis > Start’ to capture any incorrectly sized images.

View URLs that link to incorrectly sized images using the lower ‘Image Details’ tab.

The ‘Real Dimensions (WxH)’ column shows the real size of the image, while the ‘Display Dimensions (WxH)’ column shows the dimensions when actually rendered.

The ‘Potential Savings’ column highlights the differences.

Export them in bulk via ‘Bulk Export > Images > Incorrectly Sized Images’.

What Triggers This Issue

This issue is triggered when the actual dimensions of images do not match their display dimensions on the page, and there’s an estimated file size difference of 4kb or more. For example:

A 1,000×1,000 pixel image being displayed on the page with:

<img src="example-image.jpg" width="200" height="200" alt="Example Image">

How To Fix

Ideally images should not be larger than the version that’s rendered on the user’s screen. Anything larger than that results in wasted bytes and slows down page load time.

Use responsive images to serve appropriately sized images for all viewports.

For any images that are smaller than the rendered version, provide appropriately-sized versions to avoid stretched images for users.

Further Reading

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