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

The DataStore interface of the Data Store API represents a retrieved set of data, and includes standard properties for accessing the store's name, owner, etc., methods for reading, modifying and syncing data, and the onchange event handler for reacting to changes to the data.

Note: The Data Store API is available in Web Workers, from Firefox 32 onwards (Firefox OS 2.0; see bug 949325.)

Note: As of Firefox 42, the Data Store API is available to privileged homescreen apps. This is so that 3rd party homescreen apps can access the same data stores as the default homescreen app and provide equivalent functionality. See bug 1181329 for feature implementation details, and Using the Data Store API for specific code details.

Properties Read only
Returns the name of the current data store.
DataStore.owner Read only
Returns the name of the app that owns the data store.
DataStore.readOnly Read only
Returns a boolean that signifies whether the data store is read only or not.
DataStore.revisionId Read only
Returns the current revision ID of the data store.

Event handlers

DataStore.onchange Read only
Fired when a change is made to the data store, by any app that has permission to modify it.


Returns a specific record (or list of records) from the data store.
Adds a new record to the data store; if the record you are attempting to add already exists, it will throw an exception.
Updates an existing record in the data store.
Deletes a record (or list of records) from the data store
Deletes all records from the data store, leaving it empty.
Returns the number of records currently in the data store.
Opens a cursor that allows you to step through any changes that have taken place in the data store going back to a particular revision ID, and run code in response to different types of change.


In the following example, we use navigator.getDataStores to return a list of DataStore objects representing data stores on the device called contacts. Since there is only one such data store, we can access it inside the outer promise using stores[0]. The next promise uses DataStore.getLength to return the number of records in the store. If the value is 0, we populate the data store with records contained in the contactsInit object; if there is already data in the store, we run DataStore.sync to loop through any additions since the code last accessed the data store and update the data display as necessary.

navigator.getDataStores('contacts').then(function(stores) {
  stores[0].getLength().then(function(storeLength) {
    if(storeLength == 0) {
        for(i = 0; i < contactsInit.length; i++) {
    } else {
      var cursor = stores[0].sync();

Note: This code is taken from our Data Store Contacts Editor demo. Look through the code to help you understand better what is going on, and how the full code works.


Specification Status Comment
Data Store API
The definition of 'DataStore' in that specification.

The discussion concerning this API's creation happened in various Mozilla mailing lists and other places. A summary of the discussion and further pointers can be found on the Mozilla Wiki. For further feedback and questions, send mail to the dev-webapi mailing list.

Browser compatibility

Supported in Firefox OS 1.0.1.
Available in web workers in Firefox OS 2.0.

See also