Is There Any Difference Between JPG and JPEG?
JPG and JPEG are the same image format: JPEG is the official name, from the Joint Photographic Experts Group that created the standard; JPG is the everyday short form. The only file-level difference is extension length — pure historical accident.
Where the names come from
In 1992 the Joint Photographic Experts Group published the JPEG compression standard. Early DOS and Windows 3.x systems limited extensions to three letters, so JPEG became JPG. Later systems allowed longer names, and both spellings survived side by side.
The files are identical
.jpg and .jpeg are the same file format: identical headers, identical decoding. Any software that opens .jpg opens .jpeg and vice versa — you can even swap extensions by renaming, a rare case where that actually works.
Who uses which today
Windows users and everyday speech say JPG; macOS, Photoshop's format menu and formal documents lean toward JPEG. On the web there's only one name: the MIME type image/jpeg.
What it means for you
Nothing practical. A .jpg and a .jpeg from any converter are freely interchangeable; this site outputs .jpg uniformly. What actually affects quality and size is the quality setting, not the name.