WordPress image optimization: reduce bytes without wrecking image quality

Start with display dimensions

Inspect rendered sizes across common viewport breakpoints and compare them with source image dimensions. Uploading 6000-pixel originals for 800-pixel content wastes storage, processing time, and transfer unless the original serves a separate purpose.

Use WordPress responsive image srcset and sizes so each viewport can receive an appropriate image.

Choose compression and format by content

Photographs, screenshots, logos, and transparent graphics compress differently. Test WebP/AVIF support and quality against the source; an aggressive converter that damages product text or color is not an optimization.

Keep an original outside the live derivative path if future reprocessing matters.

Control generation and storage growth

Themes/plugins can register many intermediate sizes. Multiply those derivatives by the media library to estimate storage/inode cost and remove obsolete sizes carefully when themes change.

Image regeneration can be CPU/I/O intensive, so schedule bulk work away from peak traffic.

Measure page-level impact

Use browser/network tooling to see bytes, dimensions, lazy-loading behavior, LCP image timing, cache headers, and responsive source selection. Optimize the actual large visible assets first.

• Match sources to rendered sizes.
• Test format/quality visually.
• Audit generated derivatives.
• Measure bytes and LCP impact.