JPG to HEIC Converter
HEIC is a patent-encumbered format, and web browsers can read it only through add-on code but cannot write it. That means a safe, private converter in the browser cannot turn a JPG into HEIC. If you need HEIC, use your phone or computer: on iPhone and Mac, Photos and Preview can export HEIC.
If your real goal is a smaller file or wider compatibility, these tools work right here: