JPEG is the format of photographs, and most JPEGs carry far more data than the eye can use. Compresso re-encodes them with mozjpeg, which packs the same visual information into a smaller file, then checks the result against the original so nothing visible is lost. The picture you download looks identical — it just weighs much less.
Typical photos shrink by around 70%. That means faster pages, lighter email attachments and uploads that fit strict size limits, without the soft, blocky look that aggressive compression usually leaves behind.
Compress up to 20 JPG or JPEG files at once and download them one by one or as a ZIP. Everything is processed in memory and deleted the instant it is ready — your photos never leave as stored files.