Converting a set of files in one pass
Each file is decoded and written out as WebP in turn, keeping its original name and dimensions and changing only the extension. The results appear as they are finished, so you can start downloading before the whole batch completes.
JPG to WebP in short
WebP is a modern web format from Google that offers both lossy and lossless modes and supports transparency. It usually produces smaller files than JPG or PNG at similar visual quality.
Practical limits
Processing happens one image at a time inside the browser tab, so a batch of very large photographs takes a while and uses memory. If a job stalls, split it into smaller groups. The ZIP archive is assembled without extra compression, since the images inside are already compressed.