PNG and JPEG fail in different ways. Sharp synthetic graphics and photographic imagery create very different compression problems.
Ask what kind of pixels dominate
UI captures, diagrams, code screenshots, and line art often contain flat regions and sharp transitions. Photographs contain complex tonal and spatial variation. Those structures favor different compression approaches.
JPEG artifacts attack edges
At aggressive settings, JPEG's lossy compression can create ringing, blocking, and softness around text and high-contrast lines. That damage is particularly obvious in screenshots meant to teach a user where to click or what code says.
PNG pays for photographic complexity
PNG preserves pixels exactly but has no lossy model for discarding subtle photographic information. A large photo saved as PNG can therefore be dramatically larger than a visually convincing JPEG or modern lossy alternative.
Mixed screenshots need judgment
A web-page screenshot may contain both text and a huge hero photograph. PNG protects the text but pays heavily for the photo. Cropping, separating the relevant UI, or using a different format can beat a one-size-fits-all rule.
Transparency changes the choice
Traditional JPEG does not provide PNG-style alpha transparency. If the asset requires transparent edges, the comparison may involve PNG versus newer formats rather than PNG versus JPEG alone.
Compare at the intended viewing size
Export candidates, inspect the details that matter, and compare byte size. A format decision is successful when the delivered image preserves the information users need at an appropriate cost.
Sources and technical basis
Primary technical reference: W3C Portable Network Graphics (PNG) Specification, Third Edition (2025). Web-delivery sections also use MDN guidance for responsive images where relevant.
