DevConverter converts your image files online. Amongst many others, we support PNG, JPG, GIF, WEBP and HEIC. You can use the options to control image resolution, quality and file size.
JFIF is a variation of JPEG/JPG file format. The JFIF format defines supplementary specifications and was mainly used by cameras. In the meantime improvements have been made to the JPEG format and the JFIF format is mostly obsolete.