How to batch change file extensions for Windows files

Posted on February 28, 2008 at 7:07 am

Recently, I came across a problem where I had to change the file extension on a bunch of Windows files from no extension to .JPG. Someone sent me a large number of files, but for some strange reason, they had no file extension, even though they were images! Once I added the .JPG extension to the end of the file, I was able to open the images.

There are many other reasons why you may need to rename file extensions, so I’ll show you how you can change them one at a time if you have a small number of files or batch rename file extensions if you have lots of files.

If you’ve gotten an email with an attachment with no file extension, the file may look like this and when you try to open it, may ask you to choose from a list of programs:

Obviously, since there is no file extension for the file, Windows is not able to determine which program should open it. If you want to change the file extension for the file, you first need to be able to see file extensions in Windows. You can do this by going to My Computer and then going to Tools and Folder Options.

Go to the View tab and scroll down till you see the option “Hide extensions for known file types“. Go ahead and uncheck it.

If the file has no extension at all, this step may not be necessary, but I am including it because if you’re trying to CHANGE the file type from one type to another, then you need to do this. Now right-click on your file and choose Rename.

Move to the end of the name and type in .XXX or whatever the type is for the file you want it to be, i.e. .TXT for text files, .XLS for Excel files, etc. Obviously, the file has to have originally been from that program that you are changing the file extension too. In my case, the text file was from Excel and I removed the file extension, now I’ll add it back.

How to batch rename file extensions

So how do you rename multiple file extensions at once? If you have a directory full of files that need to be changed from .PNG to .JPG, it’s going to take forever to do this using the method above. That’s where you need a freeware application that can batch change file extensions for you.

Extension Renamer is a simple to use, freeware program that I have tested and contains for spyware, etc. Once you install it, it’s a piece of cake to change file extensions!

First, click Select Directory and choose the directory that contains all of the files that you want to modify. You have the option of including subdirectories also. Then you search for files with particular file extensions that you want to change. The *.* means that it will change ALL files to the new extension.

You can type in your the extension you want to change, such as .TXT in the From box along with an asterisk (*) or question mark (?) to help filter down the files. Click Search and the files that will be changed show up in the left box. Once you are satisfied, go ahead and click GO! Now all of your files will have their extensions renamed.

And that’s it! Any questions, post a comment! Enjoy!

[tag]changing file extensions, change file extension, rename file extensions, batch rename file extensions, mass rename file extensions[/tags]

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5 Responses to “How to batch change file extensions for Windows files”

Danny V said on : February 29th, 2008 at 9:59 am

I try to use it but when I click GO, I get a runtime error. That’s a shame, it could be a really good tool.

akishore said on : February 29th, 2008 at 4:57 pm

Danny, what runtime error do you get with the program? Also, what OS version are you running?

Thanks

tsberry said on : March 21st, 2008 at 2:44 am

There’s an easier way (in Vista):

Shift-right-click in the folder containing the files to be renamed

Click on “Open Command Window Here”

In the Command Window, type the DOS command for file renaming, as applicable: ie: ren *.jpg (to set the extension for all files in that directory to “jpg”)

Michael said on : March 31st, 2008 at 7:43 pm

found your site today and downloaded the program.
Works GREAT with some limitations
at least in my aapplication)
We had to change 5879 files from a printmaster “let” xtension to a “sig” xtension
it would only do 39-43 changes at a time,and in the “from” box…once it would change the number of extensions that it did…you would have to change back the origional extension that you were trying to change… ctrl+v is good. Furthermore lets say someone wrote the file name as:
j comelately.let (printmaster file) it would confuse the renamer and it would rename it:
j.let (I’m assuming because of the space between the
j and “comelately”.
Further if there is to many periods at the end of the name (ie)jcomelately dr…let (”dr” as an abbreviation for drive then more than one period) it would have difficulties.
in a perfect scenerio i think this is a wonderful program.
M

Jerry said on : April 24th, 2008 at 2:17 am

Hi! to all expert!

I have question in renaming files i.e. word or excel.

I usually do like this “right click” the mouse and choose rename… and then type a new file name without adding the extension file i.e. “.doc” for word and “.xls” for excel. And yet, everytime I rename a file I am prompted error such as “IF YOU CHANGE A FILE NAME EXTENSION THE FILE MAY BECOME UNUSABLE. ARE YOU SURE YOU WANT TO CHANGE IT?” Yes or No!

I opted YES! then it changed different icon on my file(unrecognized icon) and certainly unusable as I could not open the file and says CORRUPT! when I rename it adding the extension file it works! i.e. the new file name in excel is Monthly Report so I have to type Monthly Report.xls - it works this way. BUT previously you don’t need to add the extension file and it will autoadd/fill when you save the file.

Does anyone has an idea? I am using Windows XP Professional (OS), and MsOffice 2003. The same problem with my PC at home with O.S. Windows Vista Ultimate and 2003 MSoffice.

Any advise is very appreciated.

Jerry