How to Batch change file extensions within subfolders [duplicate]

Answer 1

If I understand correctly that you only want to rename the files from .png to .jpg, and not convert them, you could use the following batch code:

@ECHO OFF
PUSHD .
FOR /R %%d IN (.) DO (
    cd "%%d"
    IF EXIST *.png (
       REN *.png *.jpg
    )
)
POPD

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Update: I found a better solution here that you can run right from the command line (use %%f in stead of %f if using this inside a batch file):

FOR /R %f IN (*.png) DO REN "%f" *.jpg

Note that the above will process the current directory and its subdirectories. If necessary, you can specify an arbitrary directory as the root, like this:

FOR /R "D:\path\to\PNGs" %f IN (*.png) DO REN "%f" *.jpg