Xiafunge is a utility for changing the extensions of files in batch.
Visit the website for more information and a demo.
How to use: Drag one or more folders (or files) on top of the Xiafunge application in the Finder or the main window. Xiafunge immediately begins to traverse the folders and all their subfolders changing the extension of all files that match the "from extension" to the specified "to extension."
Use the Preferences window to configure the conversion. If the "from extension" is blank Xiafunge will append the "to extension" to any file without an extension. If the "to extension" is blank Xiafunge will delete the extension of any file that matches the "from extension."
With Family Sharing set up, up to six family members can use this app.