WebP is a modern image format that delivers the same visual quality as JPEG or PNG at roughly 25 to 35% smaller file sizes, and every current browser supports it. Converting your media library to WebP, while keeping originals as fallback, cuts image weight across the whole site in one move.
What causes the gap?
Years of uploads in JPEG and PNG, formats designed decades before modern compression. WordPress has supported WebP uploads since 5.8, but it does not convert your existing library, so most sites serve the old formats indefinitely.
How to check
Open the Network tab, filter Img, and read the Type column: image/jpeg and image/png everywhere means no WebP. The audit counts convertible images and estimates the total megabytes saved.
How to fix it manually
- Pick one conversion path
- Convert the library, keeping originals
- Spot-check quality on photos with fine gradients
- Confirm delivery
image/webp for supported browsers.
- Re-test page weight
How BoltAudit does it
The audit runs all of the above for you and turns it into one reviewed action.
1Finds it automatically with the count and estimated savings as evidence.
2Preview the exact change. Which images convert, projected size reduction.
3Automatic backup, originals preserved, then convert in one click.
4Roll back any time to serve the originals again.
Common questions
Do any browsers still lack WebP?
Effectively none in current use. Originals remain as fallback regardless.
WebP or AVIF?
AVIF compresses further but encodes slower and support arrived later. WebP is the safe default; AVIF is a future step.
Will my originals be deleted?
No. Conversion adds WebP versions and serves them where supported.
Does this overlap with compression?
They stack: compress sizes the image correctly, WebP changes the format. Together they carry the estimated recovery.
Run BoltAudit on your site
Free plugin · 1 site · 3 audits per month · no credit card.