Will the JPG be smaller than my WebP?
Usually not. WebP typically needs a quarter to a third fewer bytes than JPEG at the same visible quality, so the same picture as a JPG tends to be larger. Both sizes are shown so you can see the difference.
Choose the quality, see the size.
Measured against your picture
Nothing converted yet
Many upload forms and older programs still ask for a JPG, while a picture saved from a web page is often WebP. This converts it on your device, with the quality named by purpose and a colour of your choice behind clear pixels.
Usually not. WebP typically needs a quarter to a third fewer bytes than JPEG at the same visible quality, so the same picture as a JPG tends to be larger. Both sizes are shown so you can see the difference.
Balanced suits an email, a form or a web page. Best is for printing or close viewing, and Small is for a hard size limit, where the image compressor on this site can search for a quality that fits.
JPEG has no way to store transparency, so those pixels had to become a colour. White is the default. Switch the choice to black if the picture will sit on a dark surface.
No. The decoding and the encoding happen in this browser tab, and the site has no endpoint that could receive a picture.