A page can feel heavy even when its JavaScript is small. Large images deserve attention before decorative motion becomes the focus of a performance pass.
Inspect the image roles
Separate the main visible image from thumbnails and lower-page illustrations. Note the rendered dimensions and avoid serving a huge source for a small card. Preserve intrinsic dimensions or an aspect ratio to reserve layout space.
Choose loading intentionally
Prioritize the image that matters at the start of the page. Defer offscreen images where appropriate. Do not apply the same loading strategy to every asset without considering when the user needs it.
Compare the result
Measure with a consistent page and network condition before and after changes. Also inspect image quality at realistic sizes. An optimization is successful when it improves delivery without making useful visual information unreadable.
Measure images first
List each large image, its displayed dimensions, file size, format, and position in the initial viewport. The first prominent image can affect how quickly the page appears complete, while images far below the fold can usually wait. Resize source files to the actual design need.
Choose responsive delivery
Serve appropriately sized variants for common screen widths, preserve aspect ratio, and provide accurate dimensions to prevent layout shifts. Use modern compressed formats when supported and keep a readable alternative text description when the image conveys information.
Add motion after the baseline
Compare the page before and after animation on a mid-range phone and a slower connection. Avoid making essential content wait for a script or animation. Respect reduced-motion preferences and confirm the animated version does not increase layout movement or delay the main content.
An example to adapt
Compare the same page on a phone with the largest image loaded at its displayed size and again with a source several times larger. Check when the headline and main image become visible, and whether the page jumps while loading. Optimize the asset before adding motion.
Put it into practice
Choose one step from this article, try it on a representative project, and record what you learn before changing the wider workflow.
This is general editorial guidance rather than a hands-on product test; verify platform-specific details in current primary documentation.
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