Image Format Advisor
See what format every image on a page uses, and which ones are in the wrong one.
About this tool
Lists the images on a page by format and says which ones would be substantially smaller in another.
Images are usually most of a page's weight, and the format decision is where most of that weight is settled. **WebP is roughly 25 to 35 per cent smaller than JPEG** at the same visual quality and is supported by every browser in current use. AVIF is smaller still and needs a fallback for older Safari.
**A PNG photograph is the finding that costs most.** PNG is lossless — right for a logo, a diagram or a screenshot containing text, and wrong for a photograph, where the same picture as WebP is routinely a tenth of the size. Nothing on the page indicates this, and it survives every review.
Also checked: whether a `<picture>` element offers modern formats with a fallback, and whether images have `srcset` so a phone is not downloading a desktop-sized file.
File sizes are not measured — that would mean downloading every image, which this tool does not do.
Common questions
Should I use WebP or AVIF?
WebP as the default — universally supported, and 25 to 35 per cent smaller than JPEG. AVIF where the saving matters enough to add a picture element with a WebP fallback, since it encodes more slowly and older Safari cannot read it.
When is PNG the right choice?
Logos, diagrams, screenshots containing text, and anything needing sharp edges or real transparency. Never a photograph — lossless compression on a photograph produces a file many times larger for no visible benefit.
Is SVG always better for logos?
Usually. It scales to any size from one file and is often smaller. Not for anything complex — an SVG traced from a photograph can be larger than the photograph and much slower to render.
Do I need a picture element?
For AVIF, yes, so browsers that cannot read it get WebP. For WebP alone, no — support is universal enough that a plain img is fine and simpler.