Where .jfif files come from
You right-click a picture on a website, choose “Save image as”, and Windows stores it as something.jfif. It happens often with Chrome and Edge on Windows, because of how the system associates JPEG images with that extension. The picture opens fine on your computer, but when you try to upload it somewhere, the file name puzzles people and programs alike.
JFIF stands for JPEG File Interchange Format. It's simply the most common way of packaging a JPEG image, so a .jfif file is a JPG photo with an unusual extension. Nothing about the picture is different.
The problem: forms and apps don't recognize it
Many upload forms only check the extension. A profile photo field, a marketplace listing, a print shop order page or a school assignment portal may say “JPG or PNG only” and reject a .jfif file without looking inside. Some phone apps, older photo viewers and editing programs won't offer to open it either, and people you send it to may not know what to do with it.
Changing the extension to .jpg fixes all of that, because then every program knows it's dealing with a JPEG image.
A copy, not a re-encode
Because JFIF and JPG are the same format, ConvertirDocs doesn't need to decode and re-save your picture. It offers to copy the file without recompressing it, so the image data is identical to the original and no quality is lost. Re-saving a JPEG always throws away a little detail, which is why a plain copy is the better choice here.
The copy also keeps whatever photo data the file already contains. Pictures saved from websites usually carry little or none, but if you want to be sure nothing extra travels with the image, convert with recompression or pass the result through another image tool, which removes EXIF data when it reprocesses.
Stop getting .jfif files in the future
If you save images from the web often, you can avoid the problem at the source by typing .jpg at the end of the file name when the save dialog opens. Some people also change a setting in the Windows registry, but that requires care and isn't necessary. For files you already have, especially a folder full of them, converting them here in one batch is quicker.
Everything runs in your browser: the files aren't uploaded, there's no sign-up and no limit on how many you convert. ConvertirDocs is 100% free.