Will my transparent background survive the conversion?
No. JPG cannot store transparency, so transparent pixels are flattened onto a solid background. If the transparency matters, stay with PNG or convert to WebP, which keeps an alpha channel and is still much smaller than PNG.
Why did my PNG get bigger as a JPG?
That happens with flat-colour images — icons, charts, screenshots of interfaces. PNG stores large uniform areas very efficiently, while JPG spends data trying to reproduce the hard edges between them. If the file grew, the original PNG was already the better format for that image.
What quality setting should I use?
Around 80 to 90 is a good default for photos: the difference is hard to see and the file is a lot smaller. Go lower only when you have a hard size limit, and check the result — text and sharp edges are where JPG artefacts show up first.
Are my images uploaded anywhere?
No. The conversion runs entirely in your browser, so the files never leave your device and there is no upload to wait for.