Why are screenshots usually PNG while photos are JPG, and what's the difference?

Question

Weirdo · Accepted Answer

PNG is lossless, JPG is lossy. Screenshots, charts and text have sharp edges that blur and pick up colored fringes under lossy compression, so PNG keeps them clean; photos are full of gradual tones where discarded detail is hard to see, so JPG makes them far smaller.

MDN's image format guide explains the two kinds of compression: lossy discards image data to get much smaller files, while lossless reproduces the original exactly. JPEG is lossy and the most popular choice for photos; PNG is lossless and preferred when the image must be reproduced precisely.

MDN specifically recommends lossless encoding for screenshots, diagrams, logos and line art, because blurring and colored fringes around text and sharp edges are very visible, while photographs and other continuous-tone images can usually tolerate lossy compression. Save a chat screenshot as JPG and you often see a dirty halo around every letter.

Saving a phone photo as PNG does not improve it (lost detail does not come back) but can make the file several times larger. And re-editing and re-saving a JPG compresses it again each time, so it slowly degrades. Rule of thumb: text, lines or transparency go to PNG; photos go to JPG; on the web, WebP or AVIF can do both.

Why are screenshots usually PNG while photos are JPG, and what's the difference?

Lossy means trading data for size

JPG screenshots smear the text

The reverse is wrong too