The `simple-prefs` module lets you store preferences across application restarts. You can store booleans, integers, and string values, and users can configure these preferences in the [Add-ons Manager](https://support.mozilla.org/en-US/kb/Using%20extensions%20with%20Firefox#w_how-to-change-extension-settings). This gives users a consistent way to access and modify preferences across different add-ons. To define preferences and give them initial values, add a new JSON array called `preferences` to your [package.json](dev-guide/package-spec.html) file, and give it one entry for each preference: { "fullName": "Example Add-on", ... "preferences": [{ "name": "somePreference", "title": "Some preference title", "description": "Some short description for the preference", "type": "string", "value": "this is the default string value" }, { "description": "How many of them we have.", "name": "myInteger", "type": "integer", "value": 8, "title": "How Many?" }] } ## Setting Attributes ## ### Mandatory Common Attributes ### These are attributes that all settings *must* have.
Attribute Description
type The type of setting, as defined in the "Setting Types" section below.
name

An identifier for the setting. This is used to access the setting from your add-on:

console.log(require("sdk/simple-prefs").prefs.mySettingName);

This means that it must be a valid JavaScript identifier.
title This is used as a label for the setting in the Add-ons Manager user interface.
### Optional Common Attributes ### These are attributes that all settings *may* have:
Attribute Description
description This appears below the setting title in the Add-ons Manager UI.
value A default value for the setting. Depending on the setting type, this may be an integer, string, or boolean value.
### Setting-Specific Attributes ### These are settings that are only applicable to certain setting types. They are documented along with the [setting types themselves](modules/sdk/simple-prefs.html#Setting_Types). ## Setting Types ## The setting types map to the [inline settings types](https://developer.mozilla.org/en/Extensions/Inline_Options) used by the Add-on Manager. All the inline settings are supported.
Type Description Example Specification
bool Displayed as a checkbox and stores a boolean. 
{
    "description": "Does it have tentacles?",
    "type": "bool",
    "name": "hasTentacles",
    "value": true,
    "title": "Tentacles"
}
boolint

Displayed as a checkbox and stores an integer.

A boolint is presented to the user as a checkbox, but instead of storing true or false, the "on" or "off" checkbox states are mapped to integers using "on" or "off" properties in the specification.

To provide this mapping the boolint requires two mandatory attributes called "on" and "off", both of which are supplied as strings.

Note that even so, the "value" property is supplied as an integer.

 
{
    "type": "boolint",
    "name": "myBoolint",
    "on": "1",
	"off": "2",
	"value": 1,
	"title": "My Boolint"
}
integer Displayed as a textbox and stores an integer. 
{
    "description": "How many eyes?",
    "type": "integer",
    "name": "eyeCount",
    "value": 8,
    "title": "Eye count"
}
string Displayed as a textbox and stores a string. 
{
    "type": "string",
    "name": "monsterName",
    "value": "Kraken",
    "title": "Monster name"
}
color Displayed as a colorpicker and stores a string in the #123456 format. 
{
    "type": "color",
    "name": "highlightColor",
    "value": "#6a5acd",
    "title": "Highlight color"
}
file Displayed as a "Browse" button that opens a file picker and stores the full path and name of the file selected. 
{
    "type": "file",
    "name": "myFile",
    "title": "Select a file"
}
directory Displayed as a "Browse" button that opens a directory picker and stores the full path and name of the directory selected. 
{
    "type": "directory",
	"name": "myDirectory",
	"title": "Select a directory"
}
menulist

Displayed as a drop-down list. The type of the stored value depends on the default value.

The options are specified by a mandatory "options" attribute, that is an array of objects with mandatory attributes "label" and "value"

The values of the "value" attributes must be supplied as strings.

The values of the "label" attributes prefixed with "{name}_options.", where {name} is the name of the preference, are used as localization keys. If no matching entries are found, the value of the "label" attributes is used verbatim as labels.

 
{
    "name": "typeOfBreath",
    "type": "menulist",
    "title": "Type of breath",
    "value": 0,
    "options": [
        {
            "value": "0",
            "label": "Fire"
        },
        {
            "value": "1",
            "label": "Cold"
        },
        {
            "value": "2",
            "label": "Disintegration"
        }
    ]
}

  

  

		radio
		
Displayed as radio buttons.  
        The type of the stored value depends on the default value.

      
The options are specified by a mandatory "options" attribute, 
         that is an array of objects with mandatory attributes 
         "label" and "value"

      
The values of the "value" attributes must be supplied as strings.

      
The values of the "label" attributes prefixed with "{name}_options.",
          where {name} is the name of the preference, 
          are used as localization keys.
          If no matching entries are found, the value of the "label" 
          attributes is used verbatim as labels.

		
{
    "name": "alignment",
    "type": "radio",
    "title": "Alignment",
    "value": "N",
    "options": [
        {
            "value": "L",
            "label": "Lawful"
        },
        {
            "value": "N",
            "label": "Neutral"
        },
        {
            "value": "C",
            "label": "Chaotic"
        }
    ]
}

  

	

		control
		
Displays a button.

			
When the user clicks the button,
			the function listening to the on()
			function for this preference is called.


			
This type requires an mandatory attribute
			called "label" which is provided as a string.
			It is used to label the button.

		
In "package.json":
{
    "type": "control",
    "label": "Click me!",
    "name": "sayHello",
    "title": "Say Hello"
}

           
In "main.js":

var sp = require("sdk/simple-prefs");
sp.on("sayHello", function() {
  console.log("hello");
});

	




## Localization ##

Using the SDK's localization system, you can provide translated forms
of the `title` and `description` attributes. See the
[localization tutorial](dev-guide/tutorials/l10n.html#Using Localized Strings in Preferences)
for more details.


@property {object}
  *experimental* A persistent object private to your add-on.  Properties with boolean,
  number, and string values will be persisted in the Mozilla preferences system.




@function
  *experimental* Registers an event `listener` that will be called when a preference is changed.

**Example:**

    function onPrefChange(prefName) {
        console.log("The " + prefName + " preference changed.");
    }
    require("sdk/simple-prefs").on("somePreference", onPrefChange);
    require("sdk/simple-prefs").on("someOtherPreference", onPrefChange);

    // `""` listens to all changes in the extension's branch
    require("sdk/simple-prefs").on("", onPrefChange);

@param prefName {String}
  The name of the preference to watch for changes.
@param listener {Function}
  The listener function that processes the event.



@function
  *experimental* Unregisters an event `listener` for the specified preference.

@param prefName {String}
  The name of the preference to watch for changes.
@param listener {Function}
  The listener function that processes the event.


## Using the Preferences Service to Access Simple Prefs ##

If you ever need to access your simple-prefs with the `preferences/service` module,
you can do so using the extended preference name.  To get this
just prepend `"extensions." + require("sdk/self").id + "."` to the preference name `"somePreference"`.

For example, if you had a simple-pref named `"somePreference"` then you could
get its value like so:

    require('sdk/preferences/service').get(['extensions', require('sdk/self').id, 'somePreference'].join('.'))

This would give you the same value as:

    require('sdk/simple-prefs').prefs['somePreference']