What is actually happening

This is not a browser bug, even though it looks like one. When you save an image, the browser hands Windows a MIME content type — image/jpeg — and asks what file extension to use. Windows answers from a registry table. If the answer for image/jpeg is .jfif, every browser on the machine will save JPEGs that way: Chrome, Edge, Firefox, Brave, all of them.

That is also why reinstalling the browser never fixes it, and why the problem follows you from one browser to another. The setting lives in Windows, not in the browser.

The value gets changed by Windows feature updates, by image-editing or codec software registering its own file associations during installation, and occasionally by cleanup utilities that "repair" file associations. It has been reported steadily since Windows 10 build 1803.

The permanent fix (registry)

Before you start: back up the registry key. In Registry Editor, right-click the key, choose Export, and save the .reg file somewhere you can find it. Double-clicking that file restores the original value if anything goes wrong.

  1. Open Registry Editor. Press Win + R, type regedit, press Enter, and approve the User Account Control prompt.
  2. Navigate to the MIME database. Paste this into the address bar at the top of Registry Editor and press Enter: 
    HKEY_CLASSES_ROOT\MIME\Database\Content Type\image/jpeg
  3. Check the Extension value. In the right-hand pane you should see a string value named Extension. If its data reads .jfif, that is your culprit.
  4. Change it. Double-click Extension, replace the value data with .jpg, and click OK.
  5. Repeat for the related keys. Do the same for image/jpg, image/pjpeg and image/x-citrix-jpeg if they exist and also read .jfif.
  6. Restart your browser. Close every window — not just the tab — and reopen it. A full sign-out and sign-in is more reliable still.
  7. Test. Right-click any photo on a website and choose Save image as. The suggested filename should now end in .jpg.

If you cannot edit the registry

On a managed work machine the registry is usually locked. These alternatives all work without administrator rights:

  • Rename at save time. In the Save As dialog, type the filename with .jpg on the end and select All files as the type. Windows respects what you typed.
  • Use the clipboard. Right-click the image, choose Copy image, then paste into any editor and save as JPG. This re-encodes the image, so it is slightly lossy.
  • Convert after downloading. Our JFIF to JPG converter runs in the browser, needs no installation and no permissions, and does not re-compress the image.
  • Rename in bulk. If you have a folder full of them, PowerShell handles it in one line: 
    Get-ChildItem *.jfif | Rename-Item -NewName { $_.Name -replace '\.jfif$','.jpg' }

Does this happen on macOS?

Rarely. macOS resolves file types by content rather than by a MIME-to-extension table, so Safari and Chrome on macOS normally save JPEGs as .jpeg or .jpg. If you have a .jfif file on a Mac, it almost certainly arrived from a Windows machine or from a website that served it with that name.

Is anything wrong with my photos?

No. Every file saved as .jfif during this period is an intact JPEG. Renaming or converting it recovers full compatibility with no quality loss, because JFIF and JPG contain the same data.