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.
What opens 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.
Windows
- Photos
- Paint
- any browser
macOS
- Preview
- Photos
- any browser
Linux
- Image Viewer
- GIMP
- any browser
Web
- Every browser
Open a .jpg file step by step
- Confirm the file really is a .jpg. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with Photos or Paint.
- On Mac, use Preview or Photos.
- On Linux, try Image Viewer or GIMP.
- Still stuck? Convert the .jpg to PNG, which opens more widely.
Why can't I open my .jpg file?
Almost always because no installed app understands JPG. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .jpg at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
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
What is the .jpg file signature (magic bytes)?
A .jpg file starts with the hex bytes FF D8 FF E0. Programs identify JPG by those bytes, not by the filename, so a renamed file still gives itself away.
These are the documented signatures for JPG. For a full breakdown, see the JPEG file signature page.
| Hex signature | Offset | ASCII | Note |
|---|---|---|---|
| FF D8 FF E0 | 0 | - | JFIF |
| FF D8 FF E1 | 0 | - | Exif |
| FF D8 FF | 0 | ÿØÿ | 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. How sources are ranked and what is deliberately left out is set out in the methodology.