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    This feature is not on a current W3C standards track, but it is supported on the Firefox OS platform. Although implementations may change in the future and it is not supported widely across browsers, it is suitable for use in code dedicated to Firefox OS apps.

    This API is available on Firefox OS for internal applications only.


    Sets up a callback function to be notified when a specific setting's value changes.

    Note: If you want to listen for and react to any change to any setting, you can directly set a callback function using the onsettingchange property of the SettingsManager object.


    SettingsManager.addObserver(settingName, callback);


    A string specifying the name of the setting to observe. The exact list of possible strings is device-dependent. Each Gaia build can have its own list of settings. For an up-to-date list of those strings, take a look at the Gaia source code.
    The function to be called each time the value of the setting is changed. This function will receive as input a MozSettingsEvent providing details about the change that occurred.


    // Listen to changes on the wifi.enabled setting
    navigator.mozSettings.addObserver('wifi.enabled', function (event) {
      console.log('wifi.enabled: ' + event.settingValue);


    Not part of any specification yet; however, this API will be discussed at W3C as part of the System Applications Working Group.

    See also

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    Contributors to this page: Sheppy, fscholz, Jeremie, stasm, kscarfone, MHasan
    Last updated by: fscholz,