JPG vs JPEG: is there any difference?
JPG and JPEG are the same format, byte for byte. The shorter name exists only because early Windows limited file extensions to three letters. Everything else — quality, compression, compatibility — is identical.
Why two names exist
The format is JPEG — Joint Photographic Experts Group, standardized in 1992. MS-DOS and early Windows required 8.3 filenames with three-letter extensions, so .jpeg was truncated to .jpg. Mac and Unix systems never had that limit, so both spellings survived.
Every modern program treats .jpg and .jpeg identically. Renaming one to the other changes nothing about the file.
Which extension should you use?
.jpg is the safer default simply because it's more common — some poorly written upload forms only whitelist .jpg. If a site rejects your .jpeg file, rename the extension; the image itself is already valid.
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JPG vs JPEG: is there any difference? — FAQ
Yes — identical format, identical quality. JPG is just the three-letter spelling from old Windows systems.