This is the conversion to be careful with. PNG is lossless, so it will faithfully preserve every JPEG artefact already baked into your picture — and the file will get considerably larger while doing it. There are good reasons to want one anyway: a printer that demands PNG, a piece of software that refuses anything else, or a picture you are about to edit and do not want re-compressed again.
One, or up to 20 at a time. Photographs, exports, anything already saved as a JPEG.
Pixel for pixel what went in, in a format that will not compress it again.
One button per file, or the whole set as a zip.
Step by step, with screenshots: How to convert a JPG to PNG
No, and it cannot. Whatever a JPEG threw away when it was saved is gone, and no later format can reconstruct it. What PNG does is stop any FURTHER loss, which is worth having if the picture is about to be edited and saved repeatedly — but the first generation of damage is permanent.
Because PNG is not allowed to discard anything. A JPEG is small precisely because it dropped detail; asking PNG to store the result exactly means storing all the artefacts too. Four or five times the original size is normal for a photograph.
No. PNG can store transparency, but a JPEG has none to carry over, so the result is fully opaque. Making part of a picture transparent is an editing job rather than a conversion one.
If whatever you are feeding will accept it, yes. WebP is lossless too when asked to be, keeps transparency, and is substantially smaller than PNG. The only reason to prefer PNG is something downstream refusing anything else.
Free Online Image Optimizer