The `places/favicon` module provides simple helper functions for working with favicons. @function Takes an `object` that represents a page's URL and returns a promise that resolves with the favicon URL for that page. The `object` can be a URL `String` or a [`Tab`](modules/sdk/tabs.html#Tab). The platform service ([mozIAsyncFavicons](https://developer.mozilla.org/en-US/docs/XPCOM_Interface_Reference/mozIAsyncFavicons)) retrieves favicon data stored from previously visited sites, and as such, will only return favicon URLs for visited sites. let { getFavicon } = require("sdk/places/favicon"); // String example getFavicon("http://mozilla.org").then(function (url) { console.log(url); // http://mozorg.cdn.mozilla.net/media/img/favicon.ico }); // Tab example require("sdk/tabs").open({ url: "http://mozilla.org", onReady: function (tab) { getFavicon(tab).then(function (url) { console.log(url); // http://mozorg.cdn.mozilla.net/media/img/favicon.ico }); } }); // An optional callback can be provided to handle // the promise's resolve and reject states getFavicon("http://mozilla.org", function (url) { console.log(url); // http://mozorg.cdn.mozilla.net/media/img/favicon.ico }); @param object {string, tab} A value that represents the URL of the page to get the favicon URL from. Can be a URL `String` or a [`Tab`](modules/sdk/tabs.html#Tab). @param callback {function} An optional callback function that will be used in both resolve and reject cases. @returns {promise} A promise that resolves with the favicon URL.