Screenshots are a special case because they usually contain sharp text, lines and flat colors.

Use PNG for most screenshots

PNG is lossless, so text edges and UI lines stay razor-sharp. JPG's lossy compression smears fuzzy "mosquito noise" around text — ugly and harder to read.

When JPG is fine

If the screenshot is mostly a photograph (a full-screen photo, a game scene), JPG will be much smaller with no visible loss.

Keeping the file small

PNG screenshots of high-res screens can be big. Options:

Related: PNG vs JPG and reduce PNG size.