JPEG, named after the Joint Photographic Experts Group, is a widely used image format that uses lossy compression. A quality setting trades file size against visible detail, and the files use .jpg or .jpeg extensions.
Why it matters
JPEG is the default for photographs on the web and from cameras because it gives small files with good looks. It does not support transparency, and each time you re-save an edited file, more detail is lost. At low quality, blocky patches and fuzzy edges around text become visible.
WebP and AVIF often reach the same quality at smaller sizes.
Example
$ convert photo.png -quality 82 photo.jpgThis ImageMagick command saves a copy at quality 82. Compare against 70 and 90 by eye; many photos look fine in the high 70s to low 80s.
Common mistakes
- Re-saving the same JPEG repeatedly, which compounds loss; edit from the original.
- Using JPEG for logos and text, where PNG or SVG stays sharper.
- Serving camera-original files several megabytes in size.
Related
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