JPG vs JPEG: Why They're Actually the Same Format
This one has a genuinely simple answer: JPG and JPEG are the exact same image format. There's no technical difference in quality, compression, or compatibility between a file named photo.jpg and one named photo.jpeg — the difference is purely in the file extension, and it exists for a historical reason that stopped applying decades ago.
Where the split actually came from
The format's proper name is JPEG, after the Joint Photographic Experts Group that created it. Early versions of Windows (specifically MS-DOS and Windows 3.x-era systems) had an 8.3 filename limit — a maximum of eight characters before the extension, and a maximum of three characters for the extension itself. "JPEG" is four letters, one too many for that limit, so Windows systems truncated it to "JPG." Mac and Unix systems had no such restriction and kept the full four-letter "JPEG" extension. Both conventions stuck, and both are still in active use today, decades after the file-naming limit that caused the split stopped being relevant to any modern operating system.
Does the extension you use matter at all today?
Practically, no. Every modern image viewer, browser, and piece of software recognizes both extensions identically and opens the file the same way regardless of which one it's named. Renaming a .jpg file to .jpeg (or the reverse) doesn't change the file's actual content, quality, or compression in any way — it's purely a label. The only scenario where it's worth paying attention is if a specific tool or upload form is unusually strict about accepted extensions and only lists one of the two; in that case, a simple rename is all that's needed, not a real conversion.
What actually matters for JPG/JPEG files
Since it's genuinely one format under two names, the decisions that matter are the same ones that apply to any JPEG: it uses lossy compression, so a quality setting controls the size-versus-detail tradeoff, and it doesn't support transparency, which rules it out for logos or graphics that need a see-through background. If you're deciding whether JPEG (under either name) is the right format for a given image in the first place, our JPG vs PNG vs WEBP guide covers that decision in more depth.
If you ever do need to move a photo into a different format entirely — not just relabel the extension — the image converter and dedicated pages like JPG to PNG handle genuine format conversion directly in your browser.