Speed up WordPress by fixing its images
WordPress makes image bloat unusually easy to create and unusually easy to fix. The single most effective change costs nothing and takes no plugin.
What WordPress does with your upload
Upload one image and WordPress generates several — thumbnail, medium, medium_large, large, and whatever additional sizes your theme registers. Six or more files on disk from a single upload is normal.
All of them are derived from your original. Upload a 6 MB camera JPEG and WordPress produces six large derivatives of a needlessly large file. Your uploads folder grows faster than you expect, backups slow down, and every one of those derivatives is heavier than it needs to be.
Compress before uploading and every generated size inherits the saving automatically.
Prune the sizes you do not use
Most themes register image sizes that nothing on the site ever displays. Every one of them is generated for every upload, forever.
Look at what your theme and plugins register, and remove the ones nothing uses. On a site with thousands of images this alone can reclaim a substantial amount of disk and cut upload processing time noticeably.
Do this before a bulk regeneration, not after, or you will generate the files twice.
Plugins: when they help and what they cost
ShortPixel, Smush, Imagify and EWWW all work. They earn their place in two situations: you have an existing library of thousands of unoptimised images to fix retroactively, or you have a team uploading whatever comes off their phone and no way to train them.
The costs are worth knowing. Most send your images to the vendor's servers for processing — a third-party data flow you may not want, particularly for client work. Most meter usage, so a bulk run becomes a bill. And each is more PHP executing on every request, plus another thing to update and another possible conflict.
If you are the person uploading, compressing beforehand removes all of that.
WordPress and WebP
WordPress has accepted WebP uploads since version 5.8, and they behave like any other image.
Two things to check before converting a library. Some older themes hard-code the formats they expect, so test a single image first. And some managed hosts still restrict WebP at the server level — if an upload is rejected, that is usually why, and support can normally enable it.
A workflow that holds
- Resize to 1920px maximum before uploading. Larger than any theme displays.
- Convert to WebP at quality 75.
- Upload the optimised file as the source, never the camera original.
- Set a maximum upload size in your host panel so nobody can quietly upload a 12 MB file.
- Prune unused registered image sizes, once.
Five steps, four of which are one-off. After that the site stays fast without anybody thinking about it.