How to convert PNG to JPG
- Tap Choose a PNG and pick one file, or up to thirty.
- Tap Convert to JPG.
- Check the result, especially any part that used to be transparent, then save it.
Transparency has to become something
A PNG can record that a pixel is partly or completely see-through. A JPG cannot — there is no room in the format for the idea. So a converter must paint the transparent parts some colour, and a converter that never thought about it paints them black, because an untouched canvas is transparent black. That is how a cut-out signature arrives at a government portal as a black box.
This page fills with white, which is right for the overwhelming majority of cases: logos, signatures, cut-out product shots and anything that will sit on a white page. If your image is meant to sit on a dark background, converting it to JPG is the wrong move — keep the PNG.
Which format you actually want
JPG for photographs, and for anything a form asks for by name. PNG for screenshots of text, for line drawings, for logos, and for anything that needs transparency. The difference is not quality in the abstract: JPG throws away detail your eye is bad at noticing, which is a great trade for a face and a poor one for a screenshot of small text, where it leaves visible fringing around every letter.
A photograph converted from PNG to JPG will usually get dramatically smaller. A screenshot converted the same way will sometimes get larger, and will look worse. Convert when a form insists, not on principle.