JPG vs JPEG: What is actually the difference?
If you've spent more than five minutes around digital images, you've probably wondered: are JPG and JPEG the same thing, or are they different formats? The confusion is completely understandable — the internet has been inconsistent about this for decades. Here is the definitive answer.
Where the confusion started: a story about old Windows
To understand why we have both JPG and JPEG, you need to go back to the early 1990s. In 1992, an international committee called the Joint Photographic Experts Group (JPEG) published a standard for compressing photographic images. They named the format after themselves: JPEG. Files using this format were given the extension .jpeg.
Then came the problem. Early versions of Microsoft Windows, specifically MS-DOS and Windows 3.1, had a strict rule: file extensions could only be three characters long. This was a hard technical limitation of the FAT file system used at the time. Because of this limitation, Windows developers truncated .jpeg to .jpg.
Mac and Unix/Linux systems never had this three-character limit, so they kept using .jpeg. Windows moved on, gained support for longer extensions, but by then .jpg had become the dominant habit for Windows users worldwide. The result: the same format ended up with two common extensions depending on which operating system created the file.
The technical proof they are identical
Here is concrete evidence that JPG and JPEG are the same format:
| Property | .jpg files | .jpeg files |
|---|---|---|
| File header (magic bytes) | FF D8 FF | FF D8 FF |
| Compression algorithm | Discrete Cosine Transform | Discrete Cosine Transform |
| Colour space | YCbCr / RGB | YCbCr / RGB |
| Maximum quality | 100% | 100% |
| EXIF metadata support | Yes | Yes |
| Transparency support | No | No |
| Renamed .jpg → .jpeg works? | Yes, perfectly | Yes, perfectly |
Every column is identical because the format itself is identical. Renaming any .jpg file to .jpeg, or vice versa, will not affect the image in any way. The data inside the file is unchanged.
Why does this site say "JPEG" but files save as ".jpg"?
This is a deliberate and practical choice. The format name is JPEG — that is the official standard. The file extension .jpg is by far the most common in use today, especially on Windows-dominant environments. When you download a converted file from this site, it saves as .jpg because that is what the majority of software, email clients, and web platforms expect to see.
If you specifically need .jpeg files, you can rename the downloaded .jpg files — it makes absolutely no difference to the image itself.
What about HEIC — how does it fit into this picture?
HEIC (High Efficiency Image Container) is an entirely different format from both JPEG/JPG and PNG. It is not a variation of JPEG with a different extension — it is built on a completely different compression technology called HEVC (H.265), the same codec used for high-efficiency video streaming.
While HEIC produces smaller, higher-quality files than JPEG, its compatibility is limited to Apple devices and a handful of modern applications. This is precisely why converting HEIC to JPEG/JPG is so common — it transforms your photos into a format that the whole world can open without any special software.
Should I rename files to .jpg or .jpeg after conversion?
Keep them as .jpg. It is the dominant standard and what the vast majority of software, websites, email clients, and operating systems expect. Using .jpeg will not cause any technical issues, but .jpg is the safer, more universally expected choice for sharing images in 2025.