JPEG vs JPG: What's the Difference?

Is there really no difference?

Correct — and it is worth being precise about why, because the internet is full of half-answers. JPEG is a compression standard, formally ISO/IEC 10918. A file that follows that standard is a JPEG file regardless of whether its name ends in .jpg, .jpeg, .jpe or even .jfif. The extension is metadata for the operating system — a hint about which app to open — not part of the image itself.

Where the .jpg shortening came from

When JPEG arrived in 1992, the dominant desktop OS was MS-DOS / early Windows, whose filesystem allowed only a three-character extension. "JPEG" didn't fit, so it became "JPG". Mac and Unix had no such limit and happily kept "JPEG". Decades later the three-character rule is long gone, but both habits stuck — which is the entire reason you still see both today.

A quick history

• 1992 — the JPEG standard is published.
• DOS / FAT era — 8.3 filenames force .jpg on Microsoft systems.
• Mac & Unix — keep the full .jpeg.
• Today — both are universally accepted; the difference is cosmetic.

Does it ever matter which you use?

Only at the edges. SEO, image quality, file size and how browsers display the picture are completely unaffected by the choice. The only practical reasons to prefer one are:

• Consistency — pick one across a project so tooling and sorting stay tidy.
• Compatibility — a few ancient programs only recognise .jpg.
• Convention — .jpg is the more common default.

Common myths, debunked

Convinced? Then changing between them is trivial — see how to change JPEG to JPG, or go back to the overview.