/ 01JPG or JPEG? The same format.
Both extensions describe the same image format. JPEG works particularly well for photographs with many colors and gradual transitions. Its compression discards some visual information, so an 80% quality setting is a useful starting point, not a promise of identical pixels.
/ 02Choose quality for the destination.
For email and web publishing, inspect hair, foliage, and small lettering in the compressed preview. If those areas look smeared or blocky, raise quality. For a strict application limit, choose a target size; the tool may reduce pixel dimensions after searching quality settings down to 40%.
/ 03Orientation and metadata.
The browser applies embedded orientation when decoding the photo, then writes the oriented pixels into the output. Re-encoding drops source EXIF such as camera information and GPS tags. If the original is already smaller, it is kept with a metadata warning. This tool does not guarantee archival color fidelity or preserve print profiles.