WebP

WebP is an image format from Google that aims to replace both JPEG and PNG with one container. Its trick is supporting two modes: lossy compression for photographs, like JPEG, and lossless compression for graphics, like PNG, while typically producing smaller files than either at comparable quality.

It also keeps the strengths of the formats it competes with: an alpha channel for transparency (which JPEG lacks) and support for animation (like GIF, but far more efficient). For websites this adds up to faster pages and less bandwidth, which is why WebP has become common across the web. The main caveat is reach: while every current browser now decodes WebP, plenty of older desktop software, print workflows and document tools still do not, so it is not yet the safe universal choice that JPEG and PNG are.

That compatibility gap is exactly why converting WebP images into a PDF is useful, it wraps them in a format everything can open. reader.me does that conversion in the browser, so your images are repackaged without being uploaded anywhere.