What is a .jpg file?
Joint Photographic Experts Group image · Image · Joint Photographic Experts Group · 1992
JPG is the most widely used photo format in the world. Its lossy compression shrinks photographs to small, shareable files that open literally everywhere, which is exactly why so many other formats end up converted to JPG.
What is a .jpg file used for?
JPG throws away detail the eye is unlikely to notice, which is how it makes photos so small. That works beautifully for photographs and poorly for text, sharp lines or flat colour, where the compression shows as fuzz.
Because it re-compresses every time you save, repeated edits slowly degrade a JPG. For working files, keep a lossless master and export JPGs from it.
JPG has no transparency support, so images with cut-out backgrounds become white or black. Universal compatibility is its superpower.
How to open a .jpg file
The .jpg format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .jpg file.
Windows
- Photos
- Paint
- any browser
macOS
- Preview
- Photos
- any browser
Linux
- Image Viewer
- GIMP
- any browser
Web
- Every browser
How to convert a .jpg file
You can convert a .jpg file to PNG, WebP, AVIF, PDF using a conversion tool or the export menu of an app that opens it.
Convert images free: ImageConvert
.jpg file signature (magic bytes)
Programs recognise a .jpg file by the bytes at the start of the file, not by its name. These are the signatures for JPG. For a full breakdown, see the JPG file signature page.
| Hex signature | Offset | Note |
|---|---|---|
| FF D8 FF E0 | 0 | JFIF |
| FF D8 FF E1 | 0 | Exif |
| FF D8 FF | 0 | generic JPEG start |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .jpg file?
JPG is the most widely used photo format in the world. Its lossy compression shrinks photographs to small, shareable files that open literally everywhere, which is exactly why so many other formats end up converted to JPG.
Is JPG the same as JPEG?
Yes. They are the same format. The short .jpg extension is a leftover from older Windows filename limits, .jpeg is the full name.
Does JPG support transparency?
No. If you need a transparent background, use PNG, WebP or AVIF instead.
Comparisons
Related formats
Sources
Details on this page were checked against authoritative references: