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A utility to sniff preferences changes to macOS plist files


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Author: Zachary Cutlip, uid000 at gmail

prefsniff is a utility to watch macOS plist files for changes, and then autogenerate the defaults command to apply those changes. Its intended use is to have prefsniff watch a plist file while setting a system or application preference. The resulting defaults command can then be added to a shell script or incorporated into a configuration management system such as Ansible.


If you're here to simply use prefsniff and not to hack on it, there's no need to clone the git repo. You may simply install from PyPI via pip:

$ pip3 install prefsniff


prefsniff has two modes of operation; directory mode and file mode.

  • Directory mode: watch a directory (non-recursively) for plist files that are unlinked and replaced in order to observe what file backs a particular configuration setting.
  • File mode: watch a plist file in order to represent its changes as one or more defaults command.

Directory mode example:

$ prefsniff ~/Library/Preferences
PREFSNIFF version 0.1.0b3
Watching directory: /Users/zach/Library/Preferences
Detected change: [deleted] /Users/zach/Library/Preferences/
Detected change: [created] /Users/zach/Library/Preferences/

File mode example:

$ prefsniff ~/Library/Preferences/
PREFSNIFF version 0.1.0b3
Watching prefs file: /Users/zach/Library/Preferences/

defaults write orientation -string right


Additional Reading

Advanced defaults(1) Usage

An introduction to plist files and the defaults(1) command. Includes detailed explanation of each plist type and how to manipulate them with defaults.

Defaults Non-obvious Locations

An explanation of various defaults domains and where their corresponding plist files can be found on disk.

Autogenerating defaults(1) Commands

An introduction to this tool, prefsniff, and how to use it to autogenerate defaults commands.


  • Implement data and date plist types
  • Clean up output so that it can be redirected to a shell script or similar
  • Add additional output options (such as the name of a shell script to create)
  • Split utility & API
    • Make prefsniff into a python module that exports API
    • Make a separate prefsniff command-line utility that uses the API


A utility to sniff preferences changes to macOS plist files







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