What is a JPEG file?
JPEG — compressed photo
What is it?
JPEG is the most widely used photo format in the world. Its compression is described as "lossy": to reduce file size, it permanently discards information the human eye barely notices — fine variations in colour, more so than in brightness, to which our vision is far more sensitive.
In practice, the image is split into eight-by-eight pixel blocks, each converted into frequencies and then simplified. This is what causes the well-known "artefacts": small blocky squares visible around text or sharp edges when compression is pushed too far.
History & origin
The format was published in 1992 by the Joint Photographic Experts Group, a joint committee of the ISO and the ITU — hence its name. It arrived at the exact moment when the first digital cameras and the nascent web needed lightweight images.
Thirty years on, despite technically superior successors, it remains the default format for nearly all cameras and websites: its universal compatibility has withstood everything.
Why it is useful
A remarkable size-to-quality ratio for photographs: cut the file size by ten, and the eye will often see no difference at all.
It opens absolutely everywhere, without exception. No other image format can claim as much.
Limits & drawbacks
It doesn't support transparency: you can't cut out a logo on a transparent background in JPEG.
More importantly, its loss is cumulative. Every time a JPEG is re-saved, it gets recompressed: open, edit and save the same image twenty times, and it will visibly degrade. Finally, it performs poorly on flat colours and text, where it produces halos.
Practical tips
Reserve JPEG for photographs. For a logo, a screenshot, a diagram, or any image containing text, PNG will give a sharp result without halos.
Never work in JPEG: keep an original in a lossless format, and only export to JPEG at the very end. And if file size really matters, WebP or AVIF now do better at equal quality.
Convert your JPEG in seconds, on our secure servers in France.
Convert a JPEG