While renaming a bunch of photos and files one at a time is tedious, batch renaming is relatively easy. You can use ...

Finder makes it easy to rename multiple files efficiently thanks to its built-in batch rename tool, no third-party apps necessary.. To get started, select multiple files by holding Command or ...

However, there is another method. In this case, you can use your Notepad to create a batch file, which will rename all the file extensions in a specific folder and all sub-folders at once.