What does JPG stand for?
JPG stands for the Joint Photographic Experts Group, the committee that standardised the format back in 1992. The names JPG and JPEG refer to exactly the same thing — the shorter spelling simply dates from older systems that capped file extensions at three letters. Today it is one of the most universally supported image formats, readable by virtually every camera, phone, browser, and app.
How does JPG compression work?
JPG uses lossy compression built on the discrete cosine transform (DCT). In plain terms, it breaks an image into small blocks and throws away fine detail and colour information that the human eye is least likely to miss. The result is a dramatically smaller file. JPG also gives you an adjustable quality setting: turn it up for a faithful image at a larger size, or down for a smaller file that shows more compression damage.
When should you use JPG?
JPG is excellent for photographs — landscapes, portraits, and any image full of smooth gradients and subtle colour shifts. Those are exactly the images where lossy compression hides its tracks. It is a poor choice for graphics, logos, screenshots, and text, where its compression leaves visible smudging around hard edges. If you have a photo saved as a transparent PNG, you can convert PNG to JPG to shrink it for the web.
What are JPG's limitations?
JPG has no transparency — there is no alpha channel, so a transparent background fills in as solid (usually white) when you save. It also has no animation. Push the quality down and you'll see blocky artefacts around sharp edges and text. And because the format is lossy, every re-save compounds the damage — an effect called generation loss. When you need transparency back, you can convert JPG to PNG, though the detail already discarded won't return.
How does JPG compare to PNG?
The short version: use JPG for photos and PNG for graphics. JPG wins on small photographic files; PNG wins on lossless quality, transparency, and crisp edges. For a full side-by-side, see PNG vs JPG, or read what is a PNG to see how the two formats differ.
Frequently asked questions
- Is JPG the same as JPEG?
- Yes. JPG and JPEG are two names for the exact same format. The shorter .jpg extension is a leftover from older systems that limited file extensions to three letters.
- Can a JPG have a transparent background?
- No. JPG has no alpha channel, so it can't store transparency. If you need a see-through background, use PNG or WebP instead.
- Does saving a JPG over and over reduce quality?
- Yes. Because JPG is lossy, every re-save throws away a little more detail. This compounding damage is called generation loss, so keep an original copy before editing.
- Should I use JPG for screenshots and text?
- No. JPG smears blocky artefacts around sharp edges and text, which makes screenshots look fuzzy. Use PNG for screenshots, logos, and anything with hard lines.