What is a JPG file?
JPG (or JPEG) is the most common photo format in the world. It was standardised in 1992 by the Joint Photographic Experts Group, which gave it its name. The two extensions, .jpg and .jpeg, are the same format: early versions of Windows only allowed three-letter extensions.
JPEG is lossy. It splits the picture into 8 × 8 pixel blocks and stores smooth colour changes more coarsely than sharp ones, because our eyes notice them less. At quality 80–90 a photo looks the same as the original at a fraction of the size. The trade-offs: no transparency, no animation, and visible smudges around text and hard edges, which is why screenshots and logos are better as PNG.
JPG at a glance
| Full name | JPEG (Joint Photographic Experts Group) |
|---|---|
| File extensions | .jpg, .jpeg, .jpe |
| Created by | Joint Photographic Experts Group (ISO and ITU) |
| Introduced | 1992 |
| Compression | Lossy: each save throws away detail you rarely notice |
| Transparency | No |
| Animation | No |
| Typical size | About 2–5 MB for a 12-megapixel phone photo |
| Opens on | Every phone, computer, browser, printer and upload form |
| Best for | Photos you share, print or upload anywhere |
How to open a JPG file
Every device opens JPG files without extra software: double-click on Windows or Mac, or tap on a phone. If a site rejects your JPG, it is usually too big: shrink it with Compress Image or hit an exact limit with Compress Image to KB.