Set preferences, the macOS user defaults system works with both the OS and with individual applications.
Syntax
defaults [host] Actions Options
defaults help
Actions:
read [domain [key]] Print defaults to standard output
read-type domain key Print the plist type
write domain key 'value' Save a default value
write domain 'plist' Save plist (a property list) as a default:
rename domain old_key new_key Rename a domain key.
delete [domain [key]] Remove key.
(for most applications this will return the behaviour
to the original default values)
domains Print all the domains in the user's defaults system.
defaults [host] find word
Search for word in the user's defaults, and
print a list of matches.
Host Optionally you can restrict changes to a specific host
by default changes will apply to any host.
[-host hostname] Restrict to a remote machine.
[-currentHost] Restrict to the host the user is currently logged into.
Options: See below
If you change a default that belongs to a running application, the application won't see the change and might even overwrite the default.
In general you should close an application before changing its defaults, in the case of Dock and Finder defaults - restart them after applying the default with the killall command :
Restart the Dock: killall Dock
Restart the Finder: killall Finder
Data Types
defaults write ... -bool true
is not the same as defaults write ... true
The first will write a boolean value, while the second will write a string,
you can check the Data Type of an existing default with defaults read-type
Preferences are stored in a set of files under ~/Library/Preferences, however using the defaults command is much safer than manually editing a .plist file. Beginning in Mavericks, the cfprefsd daemon manages and caches updates to preference files. If you modify the file directly, the changes will not propagate through the cache managed by the daemon.
Examples:
Disable the macOS Crash reporter (quit dialog after an application crash)
$ defaults write com.apple.CrashReporter DialogType none
To re-enable the crash reporter (default)
$ defaults write com.apple.CrashReporter DialogType prompt
A long list of preferences that can be set in macOS and macOS applications can be found over in the syntax section.
Options:
Specifying domains:
domain A full domain name of the form com.companyname.appname.
defaults read com.apple.TextEdit
-app application
The name of an application:
defaults read -app TextEdit
filepath Domains can also be specified as a path to an arbitrary plist
file, omitting the '.plist' extension. For example:
defaults read ~/Library/Preferences/com.apple.TextEdit
normally gives the same result as the two previous examples.
In the following example:
defaults write ~/Desktop/TestFile foo bar
will write the key 'foo' with the value 'bar' into the plist
file 'TestFile.plist' that is on the user's desktop. If the
file does not exist, it will be created. If it does exist, the
key-value pair will be added, overwriting the value of 'foo' if
it already existed.
WARNING: The defaults command will be changed in an upcoming
major release to only operate on preferences domains. General
plist manipulation utilities will be folded into a different
command-line program.
-g | -globalDomain | NSGlobalDomain
Specify the global domain.
'-g' and '-globalDomain' can be used as synonyms for NSGlobalDomain.
Specifying value types for preference keys:
If no type flag is provided, defaults will assume the value
is a string. For best results, use one of the type flags,
listed below.
-string Allows the user to specify a string as the value for the
given preference key.
-data Allows the user to specify a bunch of raw data bytes as the
value for the given preference key. The data must be provided
in hexadecimal.
-int[eger] Allows the user to specify an integer as the value for the
given preference key.
-float Allows the user to specify a floating point number as the
value for the given preference key.
-bool[ean] Allows the user to specify a boolean as the value for the
given preference key. Value must be TRUE, FALSE, YES, or NO.
-date Allows the user to specify a date as the value for the given
preference key.
-array Allows the user to specify an array as the value for the
given preference key:
defaults write somedomain preferenceKey -array element1 element2 element3
The specified array overwrites the value of the key if the
key was present at the time of the write. If the key was not
present, it is created with the new value.
-array-add Allows the user to add new elements to the end of an array
for a key which has an array as its value. Usage is the same
as -array above. If the key was not present, it is created
with the specified array as its value.
-dict Allows the user to add a dictionary to the defaults database
for a domain. Keys and values are specified in order:
defaults write somedomain preferenceKey -dict key1 value1 key2 value2
The specified dictionary overwrites the value of the key if
the key was present at the time of the write. If the key was
not present, it is created with the new value.
-dict-add Allows the user to add new key/value pairs to a dictionary
for a key which has a dictionary as its value. Usage is the
same as -dict above. If the key was not present, it is cre-ated created
ated with the specified dictionary as its value.
Defaults allows users to read, write, and delete macOS user defaults from a command-line shell. macOS applications and other programs use the defaults system to record user preferences and other information that must be maintained when the applications aren't running (such as default font for new documents, or the position of an Info panel). Many settings can be changed through an application’s Preferences, but many settings are not shown in the GUI but can still bechanged using defaults.
In most cases the current value can be read with defaults read… it is worth checking the current setting before writing a new default (with defaults write…) just in case you want to revert to the old settings. If defaults read… returns 'does not exist' that means there is no setting currently stored, you can remove a setting with defaults delete…
User defaults belong to domains, which typically correspond to individual applications. Each domain has a dictionary of keys and values represent-ing representing ing its defaults; for example, "Default Font" = "Helvetica". Keys are always strings, but values can be complex data structures comprising arrays, dictionaries, strings, and binary data. These data structures are stored as XML Property Lists.
Though all applications, system services, and other programs have their own domains, they also share a domain named NSGlobalDomain. If a default isn't specified in the application's domain, but is specified in NSGlobalDomain, then the application uses the value in that domain.
A property list (or plist) can contain multiple values
e.g. to write a single value:
defaults write com.ss64.myapp "Default Color" '(255, 0, 0)'
to write two values (plist)
defaults write com.ss64.myapp '{ "Default Color" = (255, 0, 0);
"Default Font" = Helvetica; }';
Defaults can be structured in very complex ways, making it difficult for the user to decipher or modify them.
“I am a leader by default, only because nature does not allow a vacuum” ~ Desmond Tutu
Related macOS commands:
Awesome macOS Command Line - A large collection of macOS defaults.
Show hidden files.scpt - Toggle the display of hidden files in Finder (will restart finder)