A JPG file is a compressed image file, and it's the most common way photos are stored and shared on the internet. The name comes from the group that invented it: JPEG stands for Joint Photographic Experts Group, the committee of engineers that published the standard in 1992. So "JPG" and "JPEG" both stand for the same thing, and they are the same format. More on that spelling quirk in a moment.
If you've ever taken a picture on your phone, downloaded an image from a website, or attached a photo to an email, you've almost certainly handled a JPG. It's everywhere because it does one job extremely well: it shrinks big, detailed photographs down to small files that still look good.
What does JPG stand for, and why two spellings?
Both .jpg and .jpeg point back to the Joint Photographic Experts Group. The format itself doesn't care which extension you use.
The reason you see two spellings is historical. Early versions of Windows (and the DOS system underneath it) limited file extensions to three characters, so the format got shortened to .jpg. Mac computers and Unix systems had no such limit, so they kept the full .jpeg. Both open the same way in every modern program. If you want the longer version, we cover it in our guide on JPG vs JPEG.
How JPG compression works, in plain language
Here's the core idea. A photo contains far more detail than your eyes can actually notice. JPG takes advantage of that by throwing away the information you're least likely to see, then packing what's left into a much smaller file.
This is called lossy compression. "Lossy" means some data is permanently discarded when the file is saved. In exchange, the file gets dramatically smaller. A raw photo straight off a camera sensor might be 30 megabytes; the same image saved as a JPG might be 3 megabytes and look nearly identical on screen.
The format is especially clever about two things. It groups together areas of similar color, since our eyes are more sensitive to brightness than to slight color shifts. And it simplifies fine, high-frequency detail that we tend to gloss over anyway. You control how aggressive this is with a quality setting, usually a number from 0 to 100. A high setting keeps most of the detail and makes a larger file. A low setting squeezes harder and can introduce blocky patches or fuzzy halos around sharp edges, known as compression artifacts.
One thing to keep in mind: every time you open a JPG, edit it, and save it again, the file is re-compressed and loses a little more. It's usually invisible once or twice, but it adds up. If you plan to edit an image many times, keep a master copy in a lossless format and export to JPG only at the end.
What JPG is good at (and what it isn't)
JPG shines with photographs and any image full of smooth gradients and millions of colors: sunsets, portraits, landscapes, product shots. That's exactly the content its compression was designed for.
It's a weaker choice for a few specific things:
- Graphics with sharp edges and flat color, like logos, screenshots of text, or line art. JPG tends to smudge crisp edges. PNG handles these better.
- Images that need transparency. JPG has no transparent background. If part of your image needs to be see-through, you need PNG or WebP.
- Master files you'll edit repeatedly. Because each save loses a bit of quality, JPG isn't ideal as a working file.
For everyday photos meant to be viewed or shared, though, those limits rarely matter.
| Feature | JPG |
|---|---|
| Compression | Lossy (smaller files, some detail lost) |
| Transparency | No |
| Best for | Photographs, colorful images |
| Weak at | Text, logos, sharp edges, transparency |
| Support | Universal, opens on any device |
Where you'll find JPG
Pretty much everywhere. Digital cameras and smartphones save photos as JPG by default (or convert to it easily). Websites use it for photo content to keep pages loading fast. Email attachments, online forms, marketplace listings, ID uploads, and printed photo orders all commonly expect JPG. Its biggest strength beyond compression is compatibility: a JPG opens on any phone, computer, tablet, or web browser without special software.
How JPG compares to PNG and WebP
JPG isn't the only image format, and it's not always the right one.
PNG uses lossless compression, so it keeps every pixel exactly. That makes files larger, but it's the better pick for logos, screenshots, text, and anything needing a transparent background. For a full breakdown, see JPG vs PNG.
WebP is a newer format from Google that can produce smaller files than JPG at similar quality, and it also supports transparency and animation. Support is now broad across modern browsers, though JPG still wins on universal compatibility with older software and devices.
A simple rule: use JPG for photos, PNG for graphics and transparency, and WebP when you want small files on the modern web and know your audience's software supports it.
Working with JPG files
If you have an image in another format and need a JPG, you can convert it in seconds with our free online JPG converter. It runs in your browser, so your files never get uploaded to a server. Want to go deeper on the technical side, including color profiles and metadata? Our JPG format guide covers it.
The short version: a JPG is a smart, compressed photo file named after the expert group that created it back in 1992. It trades a little invisible detail for a much smaller file, and that trade is why it became the default image of the internet.