Optimize WordPress images by checking both the uploaded source and the variants delivered by the theme or image service. Pre-compressing an upload can help, but it does not ensure the front end chooses an appropriate size. Begin with a representative page and inspect the actual request before changing every image in the Media Library.
Confirm format support on the host
WordPress added AVIF support in version 6.5, conditional on the hosting image-processing environment. Browser display support alone is not enough. Upload a sample and check that the site can generate the required derivatives. Keep an accepted JPEG or PNG workflow when a host, plugin or downstream service cannot handle the preferred format.
Prepare a useful source, not only a tiny thumbnail
Choose the upload dimensions around the largest legitimate placement, including density or zoom needs. Do not overwrite the archival original. An excessively small source cannot generate a sharp large variant later; an unnecessarily huge source adds storage and processing work.
Inspect the selected front-end image
Illustrative check: open a product page on a narrow viewport and inspect the requested image URL and dimensions. Compare it with the desktop request. If the same oversized file appears everywhere, examine theme image selection and responsive sizes before aggressively recompressing the source.
Plugins and CDNs may change formats or generate variants, so avoid assuming your local export is delivered unchanged. Verify actual content type, transfer size and appearance.
Treat loading and layout separately
Do not lazy-load the LCP image merely because a plugin offers a global toggle. Reserve image space and use lazy loading for appropriate secondary media. After deployment, compare request timing and page layout under consistent conditions. A faster image download cannot by itself repair slow server HTML responses or render-blocking page work.