You can just rename jfifs to jpegs

pcgamer.com:

I don't know about you, but I'm tired of the internet of the 2020s assaulting me with new, unwanted file formats. Who asked for webps to infiltrate our Google Image search results? I have no use for that trash! Until a somewhat recent update I couldn't even open them in Photoshop, a program that exists solely to open and modify images. I want to throw my monitor out the window every time I go to download an image and find out it's a webp, and I have a similar reaction whenever I come across a jfif. But here's a quick tip you may not know: you can just rename a jfif and get on with your life.

Here's all you need to know about jfif images: They're jpegs.

Well, basically. You can read the long, technical explanation of how the JPEG File Interchange Format works, but the short version is that JPEG is an image compression standard, and JFIF is a file format that uses that standard. Even that is probably more than you need to know about jfifs if your only experience with them is trying to save an image off the internet and going «ugh, what the hell is this thing?»

Some programs react that way, too. They should know that despite that .jfif file extension, the underlying data is just a jpeg, the same image format we've been using since time immemorial. Discord, for example: 

The solution to this problem is so blissfully easy, it really does seem too good to be true: You can just rename the file. No image conversion necessary. Do not open a jfif in MS Paint or Photoshop and bother resaving it. Just click on the file name, press backspace four times, type jpg (or jpeg), and hit Enter. You now have a perfectly usable image. The two in the screenshot above are the exact same files, just with one quickly renamed.

I wish I could offer