A .jfif file is already a JPEG with an odd name. This page renames it to .jpg and copies the picture byte for byte — no re-encoding, no quality lost — unless you ask for a change that needs one.
Why nothing needs converting
JPEG is the compression; JFIF and EXIF are two ways of wrapping it in a file. A camera usually writes the EXIF wrapping, a browser or an editor often writes JFIF, and both have been called .jpg for thirty years. The .jfif extension appears when Windows tells the browser that this is the name for JPEG files.
So the honest conversion is a rename. Re-encoding would decode the picture and compress it again, which spends a generation of quality and buys nothing.
Step by step
- Drop the .jfif files on the panel. Each row confirms from the bytes that it is a JPEG.
- Leave Lossless on (Quality panel). Choose .jpg or .jpeg as the extension.
- Optionally drop the location or all metadata in Metadata, or write a DPI label in Size — still lossless.
- Press Download. Each card reads Lossless — compressed picture copied byte for byte.
What can still change without re-encoding
The metadata switches (drop the location, drop everything) and the DPI label all live in segments around the compressed picture, so they are rewritten without touching it. Size, quality and background controls need the encoder; when Lossless is on they do not apply to JPEG sources, and the panel says so.