Data URLs, URLs prefixed with the data: scheme, allow content creators to embed small files inline in documents. They were formerly known as "data URIs" until that name was retired by the WHATWG.
When I was using the tool to convert an
.mp3 file from a given URL, I needed to add the mime type manually to the resulting URI. In my case it was audio/mp3, like in
The general format of a data URL is
data:[<mime type>][;charset=<charset>][;base64],<encoded data>