Most sites upload photographs straight from a camera
A phone photograph is often several megabytes and four thousand pixels wide, displayed at eight hundred. That waste is repeated across every page.
Resizing before upload is the single most effective speed improvement available to most sites.
The routine
- Resize to roughly twice the largest displayed size
- Compress — quality around 80% is usually indistinguishable
- Serve modern formats where the browser supports them
- Lazy-load anything below the fold
- Set explicit dimensions so the layout does not jump
Two thousand pixels wide is plenty for a full-width image on almost any site. Four thousand is a file nobody benefits from.
Alt text is not optional
Every meaningful image needs a description of what it conveys. Decorative images should have empty alt text so they are skipped rather than announced.
It is an accessibility requirement, it helps search, and it takes ten seconds per image at upload time.
Keep the library tidy
- Descriptive filenames before uploading, not IMG_4821
- Delete unused images periodically
- Avoid re-uploading the same image several times
- Check for orphaned files after removing pages
Where a CDN helps
An image-heavy site with visitors spread geographically benefits noticeably from a CDN. A local business with modest images benefits less.
It is not a substitute for sizing and compressing, which should come first regardless.