JPG / JPEG

JPG (also written JPEG, for Joint Photographic Experts Group) is the most common format for photographs and one of the most common image types embedded in PDFs. It uses lossy compression, throwing away detail the eye is least likely to notice, to make photo files dramatically smaller.

That trade-off is exactly why JPG dominates for photos: a high-quality picture that would be huge as raw data becomes a manageable file with little visible loss. The catch is that compression is destructive and cumulative. Re-saving a JPG over and over degrades it, and the format handles sharp edges, like text or line art, poorly, producing fuzzy halos.

For scanned documents and photos inside a PDF, JPG is usually the right call and keeps file size in check. For screenshots, logos, or anything with crisp edges and flat color, PNG is the better choice.