Convert JFIF to JPG, and know when you don't need to
Your .jfif file is already a JPEG. JFIF is the container JPEG has used since 1992: same bytes, same decoder, a different extension. Windows hands you that extension because of a registry entry that maps image/jpeg to .jfif, not because anything is wrong with the photo. Renaming photo.jfif to photo.jpg genuinely works, and we would rather tell you that than pretend you need a tool.
What renaming does not fix is a folder full of files, an extension that lies about what is inside, a photo that opens on its side, or an original that is simply too big. A 13.4 megapixel photograph in our test set went from 4.82 MB to 1.88 MB at the default level, a cut of 60.9 percent, in about a third of a second.
Why your computer saves pictures as .jfif
When a browser saves an image, it asks Windows which extension belongs to the MIME type image/jpeg. On many installations the registry answers .jfif. That answer travels with the file, so the same photo that would have been photo.jpg on another machine arrives as photo.jfif on yours. The pixels, the compression, and the colour data are identical either way. Older software that checks the extension instead of the file contents is what refuses to open it.
Portrait photos come back upright, and stay that way
A phone writes the way it was held into the file as an EXIF orientation tag instead of rotating the pixels. Converters that ignore the tag hand you a sideways photo. Converters that apply it but leave the tag in place are worse: the pixels get turned once by the converter and a second time by whatever opens the file, so the photo ends up rotated the wrong way in Chrome, on an iPhone, and in Windows Photos.
Here the rotation is written into the pixels and the tag is then cleared, so nothing turns the image again. A 1200 by 800 test photo carrying orientation tag 6 came back as 800 by 1200, upright, with the tag gone and a note on the result saying the orientation was applied.
When renaming is enough
If you have one file and it opens fine in your photo viewer, rename it and move on. Use a converter when you are dealing with a batch, when you do not trust the extension, when the photo is sideways, or when you want something else out of the process: a smaller file, a different format, or a consistent naming pattern across a folder.
What the conversion actually changes
The image is decoded and encoded again, so the result is not byte identical to what you uploaded. On our test photograph the average pixel moved 1.90 out of 255 at the default level. That is invisible on screen, but it is not zero, and it is worth knowing if the file is your only master copy.
Three levels cover the size question without an arbitrary slider. Best quality uses JPEG quality 92 and produced 3.82 MB from the test photo. Recommended uses quality 82 and produced 1.88 MB. Smallest uses quality 62 and produced 1.23 MB. The level you picked and the quality number it resolved to are both shown with the result, so a conversion can be repeated later with the same settings.
Quality 100 makes the file bigger, not better
Asking a JPEG encoder for quality 100 is the most common way to waste space. We measured it on the same photo: the output was 8.51 MB from a 4.82 MB original, 76.5 percent larger, and it recovered nothing that the first round of compression had already discarded. Quality 92 is the sensible ceiling.
Colour, and what happens to your file
The embedded colour profile is kept by default, so a photo shot in a wide gamut does not come back oversaturated. If you need plain sRGB instead, one setting converts it properly rather than reinterpreting the numbers. Convert one file or a whole batch, and several files come back as one ZIP with the original names carried over. There is no account, no watermark, and finished files are deleted an hour after the conversion.
What you get
- A real .jpg file, decoded from the actual contents of your upload rather than its extension
- EXIF orientation applied to the pixels and the tag then cleared, so nothing rotates the photo a second time
- Three named quality levels, plus the exact quality number used, shown with the result
- Original dimensions, unchanged: this is a converter, not a resizer
- The embedded colour profile kept, or a clean conversion to sRGB when you ask for it
- Free, no account, no watermark, and files deleted after one hour
What's next?
Need a lossless format for further editing instead? Use JFIF to PNG. If the file size is the only problem and the format is fine, Compress JFIF keeps the format and cuts the bytes. To turn a set of images into one document, JFIF to PDF does it in a single step.