What Is JPG? Everything You Need to Know About the JPEG Format

JPEG was standardised in 1992 by the Joint Photographic Experts Group and has been the default photographic format ever since. Its discrete cosine transform compression was a genuine breakthrough for 1992 hardware, and three decades of universal support have made it effectively un-replaceable: JPG is the one image format you can hand to any person, any device or any upload form and be certain it will open. Modern codecs beat it substantially on file size, but none of them beat it on reach.

Compression: Lossy DCT. Transparency: None — no transparency at all. Animation: Not supported. Colour: 8-bit per channel, sRGB. Typical file size relative to WebP: 25-35% larger than a WebP of the same visual quality.

Universal — every device, app and upload form ever made. This is usually the deciding factor when choosing between JPG and WebP — WebP renders in every browser but is uneven in desktop software, while JPG has a very different support profile.

Converting JPG to WebP is the cheapest page-weight win available. At matched visual quality WebP lands 25-35% smaller, which shows up directly in Largest Contentful Paint and your Core Web Vitals scores. Both formats are lossy, so re-encoding adds a small amount of generational loss — invisible at quality 80 and above, but a reason to convert from the highest-quality source you have rather than from an already-compressed copy.

This is the single most common reason people convert anything on this site. You right-clicked an image on a web page, saved it, and got a .webp that Photoshop, Word, your photo printer or a job-application upload form flatly refuses. JPG is the universal answer — nothing rejects a JPG. Expect the JPG output to be 25-35% larger than a WebP of the same visual quality — that difference is the price of getting a format the destination will actually accept.