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Why Windows saves your JPEGs as .jfif, and the one registry value that fixes it

#windows #powershell #beginners #productivity

You right-click a photo in Chrome or Edge, choose Save image as, and Windows offers photo.jfif. Then the upload form at work, the visa portal or an older app says the file type is not allowed.

The file is fine. Here is what is going on and how to stop it.

JFIF is just a JPEG

JFIF (JPEG File Interchange Format) is the wrapper most .jpg files have always used. A .jfif and a .jpg from the same source both start with the bytes FF D8 FF E0, and a few bytes later the letters JFIF. Same format, different ending.

So for one file, renaming photo.jfif to photo.jpg is enough. Nothing is converted and nothing is lost.

Why the browser picks .jfif

When a browser saves a download whose type is image/jpeg, it asks Windows which file ending belongs to that type. Windows looks it up in the registry here:

HKEY_CLASSES_ROOT\MIME\Database\Content Type\image/jpeg
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The value named Extension holds the answer. On many machines it says .jfif: an app or an update set it at some point, and every browser on that machine follows it. You can check yours in PowerShell:

reg query "HKCR\MIME\Database\Content Type\image/jpeg" /v Extension
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On the Windows 11 laptop I wrote this on, it printed .jfif.

The fix

Open PowerShell as administrator and run:

reg add "HKLM\SOFTWARE\Classes\MIME\Database\Content Type\image/jpeg" /v Extension /t REG_SZ /d .jpg /f
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Close and reopen the browser. Save image as now offers .jpg.

If you cannot change the registry (a work laptop, a shared PC), renaming each file still works.

Many files at once

A folder full of .jfif files can be renamed with one line of PowerShell, run inside that folder:

Get-ChildItem *.jfif | Rename-Item -NewName { $_.BaseName + '.jpg' }
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Only the names change, so the pictures stay exactly the same.

On a phone, or without a terminal

For a phone, or when you just need a couple of files fixed in a browser, we made a small free tool that gives a .jfif the .jpg ending without saving the picture again, so it keeps all of its quality (it also takes out hidden details such as the location): JFIF to JPG. It works without an account.

Written with AI assistance. The commands were run and checked on Windows 11.

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