Google Analytics without cookies

cookieless-ga.js

// https://medium.com/swlh/how-to-use-google-tag-manager-and-google-analytics-without-cookies-7d041c73cc76
// https://developers.google.com/tag-manager/devguide
(function() {
    window.dataLayer = window.dataLayer || [];

    var GA_MEASUREMENT_ID = "UA-XXXXXXXXX-X",
        GA_LOCAL_STORAGE_KEY = "ga:clientId",
        clientId = localStorage.getItem(GA_LOCAL_STORAGE_KEY),
        gtag = function() {
            dataLayer.push(arguments);
        };

    gtag("js", new Date());

    // checks if user was already connected and loads client_id from localstorage
    if (!clientId) {
        // creates client_id and saves it in localStorage -> currently random number better would be a uuid
        localStorage.setItem(GA_LOCAL_STORAGE_KEY, clientId = Date.now() + "-" + Math.random());
    }

    // creates new tracker with same client_id as the last time the user visited
    gtag("config", GA_MEASUREMENT_ID, {
        // send_page_view: true, // it's true by default
        client_storage: "none", // don't use cookies
        client_id: clientId,
    });
})();