JFIF files hold ordinary JPEG data. This page decodes yours and writes a lossless PNG — locally, with no upload and nothing to install.
JFIF is not a rival image format — it stands for JPEG File Interchange Format, the container ordinary JPEG data has always been stored in. Windows occasionally saves pictures copied out of a browser with a .jfif extension, and the unfamiliar name alone is enough for an upload form, a design tool, or a colleague to reject the file. When the place you need to put it asks specifically for PNG, this page handles it in one step.
The tool decodes the JPEG data inside your JFIF and writes the resulting pixels into a PNG, which stores them exactly. Everything the decoder produced survives — but that is where the losslessness begins, not where your file started. JPEG compression already discarded detail when the picture was first saved, and PNG cannot bring it back; soft edges and blocky artifacts in the JFIF are copied into the PNG with perfect fidelity. JPEG also has no alpha channel, so the PNG comes out fully opaque. Converting does not give an image transparency it never had.
PNG output is almost always bigger than the JFIF it came from, often several times over, because lossless compression must store every pixel of a photograph instead of approximating it. That is normal rather than a sign of trouble, and each result is shown next to its original size. If all you actually need is a file name the world accepts, the JFIF to JPG page renames yours without re-encoding a single pixel and keeps it small. Either way the work happens in this tab: no upload, no account, and batches of any size with a ZIP at the end.
The PNG stores every pixel the decoder produced, so nothing is lost in this step. It cannot restore detail that the original JPEG compression had already thrown away.
JPEG compresses photographs by approximating them; PNG stores them exactly. A file several times larger is the expected outcome.
No. There is no transparency in JPEG data, so the converted PNG is fully opaque. PNG supports an alpha channel, but a JFIF source has none to carry over.
If you only need a normal file name, yes — the JFIF to JPG page passes the bytes through untouched, so nothing is re-encoded and the file stays small.
No. The decode and the PNG encode both run in a Web Worker in this page, so your images never leave your device.