Disable the File Extension Change Warning in Mac OS X

Apr 11, 2012 - 5 Comments

File Extension change warning in 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.

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Posted by: William Pearson in Mac OS X, Tips & Tricks


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  1. Napoleon Wilson says:

    Just open the Finder preferences advanced tab and uncheck Show warning before changing an extension

    much simpler

  2. [...] activar este truco hay que entrar en la Terminal y poner este [...]

  3. Austin Hunt says:

    Thanks! This is the best tip yet for developers who do a lot of html and php extension changes.

  4. [...] A good tip from OSXDaily.com: Disable the File Extension Change Warning in Finder. [...]

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