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JPEG image Reference

A .jpg file contains a photo or other raster image with JPEG compression. The compression is lossy: a smaller file costs some image quality. Digital cameras and web sites use the format heavily. The compression ratio is adjustable. The extension .jpeg means the same format.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.