I have a folder of thousands of files in different formats but without any extensions. I know how to detect unknown file types using the tools such as TrID - File Identifier and DROID: file format identification tool, but I need to bulk rename the files and add the appropriate extension to them in Windows. I searched a lot and couldn't find a working solution for that. I couldn't find any duplicate topic here in superuser. Thanks.


I suggest using rename master . it's user friendly and power full

rename master

another Power full tools :

Bulk Rename Utility

Ant Renamer

ReNamer Lite

  • No software from that site would be recommended to be downloaded as the site doesn't appear to support HTTPS (some pages load, some don't when HTTPS is forced) and none of the downloads can be downloaded via HTTPS, nor is a GPG signature or SHA256 or greater hash offered to verify the download's integrity (even with those, if the page they were on was not protected by HTTPS, those could also not be trusted) - same is true for Bulk Rename Utility (e.g. there's no way to determine if the payload hasn't been compromised by a MITM)
    – JW0914
    Feb 5 '21 at 12:44
  • Thanks MohammadReza. From this list, only the ReNamer Lite had file type detection feature. The rest was not working. Trid command line had a more accurate type and extension detection rate. I will share screenshots of all these tools.
    – eArmin
    Feb 5 '21 at 18:14

TrID does that, although it is not perfect. It analyzed correctly my DOCX file, but renamed it to .tmdx for some reason:

enter image description here

  • Thanks Harry. Trid did the job perfectly. I wonder why I haven't find the documents. Sorry, I can't vote for the answer because of my reputation.
    – eArmin
    Feb 5 '21 at 18:12

I almost tried all the tools in the answers. Trid command line had the most accurate output, and ReNamer Lite had the fastest result with more renaming features, ReNamer failed in detecting mp4 and mov files. Bulk Rename Utility doesn't have Filetype and Extention detection feature but has a lot of helpful options for bulk renaming.

Trid Output Result, Took about 2min for 60 files

ReNamer Lite, Took 5 seconds for 60 files, failed in detecting .mov and .mp4 files

Bulk Rename Utility, Lack of file type detection


You can use a tool called Exiftool.

Download here: https://exiftool.org/exiftool-12.17.zip

Unzip, rename from exiftool(-k).exe to exiftool.exe, copy to c:\windows\system32

Let's say the folder with files that have wrong or no fileextension is C:\My Files:

Open command prompt and:

exiftool -r "C:\My Files" "-Filename<%f.$filetypeextension"
  • 1
    Never copy any third-party program into %WinDir% - it's a security risk and as soon as sfc is run, the program will be removed. (once that bad advice is removed, I'll remove my downvote; also, please use correct markdown for monospaced code and weblinks)
    – JW0914
    Feb 5 '21 at 12:49

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