Info: [rfc2397](https://tools.ietf.org/html/rfc2397). The Wikipedia's [article](https://en.wikipedia.org/wiki/Data_URI_scheme). Examples: `data:image/gif;base64,...` `data:image/png;base64,...` Maybe other image formats? Of course, it can be implemented as a custom uploader, but a built-in feature is preferable. :)