What is the JPG format?

Overview

JPG (JPEG) is a lossy format standardized in 1992. It drops information the human eye is less sensitive to, making photos very small. It is the format cameras and smartphones save by default, so it is the one you meet most often.

Because it is lossy, quality drops slightly every time you re-save, and it doesn't support transparency. Converting a transparent PNG to JPG means the transparent areas must be filled with some color, so this site lets you pick the background color yourself.

History

JPEG takes its name from the Joint Photographic Experts Group, which published the standard (ITU-T T.81) in 1992. It uses the discrete cosine transform (DCT) to exploit the fact that our eyes are less sensitive to small differences in color.

It became the de facto standard for photos with the spread of digital cameras, and most cameras and smartphones still save it by default. The extensions .jpg and .jpeg are the same format.

Pros

• Stores photos in very small files
• Opens on virtually every device and service
• Quality setting lets you trade file size against quality

Cons

• No transparent background
• Quality degrades each time it is re-saved
• Blocky artifacts appear around sharp text and line art

Best used for

• Sharing photos
• Blog and online-shop product photos
• Email attachments
• Images for official or school submissions

Compatibility

The most compatible photo format. Old software, print shops and upload forms mostly ask for JPG.