I set the default app to open the files with special file extension by mistake: the app could not open them at all for they're only file fragments (or, say, no app can until I combine them as one file).
So I want to clean the settings of default app (set no default app), but no solutions found. Any ideas? Hope for your answers!


It's free, and configurable per extension.


  • The app you mentioned sounds interesting. I tried it and set the default app to 'DoNothing', then uninstall it; then the default app is null, and no app will try to open the 'special' files. Nice solution, but not the best one. Thanks for your answer! – kenmux Oct 21 '14 at 2:49

For changing default app (no option to clean the setting tho):

  1. If you don't have a file with that specific extension - create one.
  2. Right click on it -> get info.
  3. Set "Open with" and click "Change All" button right under it.

All files with that extension will now be opened by that app.

  • OMG. Then I could not clean the setting of default app? What sad story. – kenmux Oct 21 '14 at 2:21
  • I have a question: where is the setting stored? a plist file? or not? – kenmux Oct 21 '14 at 2:23
  • I guess so, but couldn't find the correct file atm. Anyway, IIRC preferences are now cached and I've seen some people having problems figuring out proper plist files for their needs :/ – Marek Bettman Oct 22 '14 at 1:39

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