Round all four corners together or shape each one on its own — including elliptical corners, which take two radii and give you a soft oval rather than a quarter circle.
An elliptical corner takes two radii — horizontal, then vertical after the slash. It is how you get a soft oval corner rather than a quarter circle.
The CSS
border-radius: 24px;
Set what you want and the result appears as you go. Nothing needs uploading because there is nothing to upload — you are describing what to make, not sending us anything.
Your browser does all the work locally, using your own operating system where randomness is involved. Nothing is requested from a server, so nobody else has a copy of what you made.
Take the result to your clipboard or save it as a file. Nothing is kept — refresh the page and it’s gone, so save what you need before you leave.