Disable the File Extension Change Warning in Mac OS X

Assuming you have file extensions shown in the OS X Finder, attempting to change a file extension causes a warning dialog with a confirmation box to appear. This is annoying if you know what you’re doing and you have a compelling reason to change extensions, so let’s turn it off using the command line and defaults write.

First, open the Terminal, located within the /Applications/Utilities/ directory, then copy and paste in the following command:

defaults write com.apple.finder FXEnableExtensionChangeWarning -bool false

Follow that up by relaunching the Finder with killall:

killall Finder

To reverse the change and get the warning back when you attempt to change file extensions, use the following defaults write command:

defaults write com.apple.finder FXEnableExtensionChangeWarning -bool true

Kill the Finder again for changes to take effect.