All angular services are singletons:
Docs (see Services as singletons): https://docs.angularjs.org/guide/services
Lastly, it is important to realize that all Angular services are application singletons. This means that there is only one instance of a given service per injector.
Basically the difference between the service and factory is as follows:
app.service('myService', function() {
// service is just a constructor function
// that will be called with 'new'
this.sayHello = function(name) {
return "Hi " + name + "!";
};
});
app.factory('myFactory', function() {
// factory returns an object
// you can run some code before
return {
sayHello : function(name) {
return "Hi " + name + "!";
}
}
});
Check out this presentation about $provide: http://slides.wesalvaro.com/20121113/#/
Those slides were used in one of the AngularJs meetups: http://blog.angularjs.org/2012/11/more-angularjs-meetup-videos.html