diff --git a/user-id-autofiller/user-id-autofiller.user.js b/user-id-autofiller/user-id-autofiller.user.js
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@@ -0,0 +1,71 @@
+// ==UserScript==
+// @name        SEDE User ID Autofiller
+// @namespace   https://github.com/Glorfindel83/
+// @description Automatically fills SEDE parameters 'AccountId' and 'UserId'
+// @updateURL   https://raw.githubusercontent.com/Glorfindel83/SE-Userscripts/master/user-id-autofiller/user-id-autofiller.user.js
+// @downloadURL https://raw.githubusercontent.com/Glorfindel83/SE-Userscripts/master/user-id-autofiller/user-id-autofiller.user.js
+// @author      Glorfindel
+// @version     0.1
+// @match       *://data.stackexchange.com/*/query/*
+// @grant       GM_xmlhttpRequest
+// @grant       GM.xmlHttpRequest
+// ==/UserScript==
+
+/* global $ */
+
+(function() {
+    'use strict';
+
+    $('#query-params input').each(function() {
+        let input = $(this);
+        let name = input.attr('name');
+        switch (name.toLowerCase()) {
+            case 'accountid':
+                // Fetch global account ID
+                GM.xmlHttpRequest({
+                    method: 'GET',
+                    url: 'https://stackexchange.com/users/current',
+                    onload: function (data) {
+                        let matches = /\/users\/(\d+)\//g.exec(data.finalUrl);
+                        // Fill input field
+                        input.val(matches[1]);
+                    }
+                });
+                break;
+            case 'userid': {
+                // Determine current site
+                let queriesURL = $('#header nav a[title=Queries]')[0].href;
+                var site = /https:\/\/data.stackexchange.com\/(.*)\/queries/.exec(queriesURL)[1];
+                if (site == 'meta.stackexchange' || site == 'stackapps' ||
+                    site.endsWith('stackoverflow') ||
+                    site.endsWith('superuser') ||
+                    site.endsWith('serverfault') ||
+                    site.endsWith('askubuntu')) {
+                    site += '.com';
+                } else if (site.endsWith('mathoverflow')) {
+                    site += '.net';
+                } else if (site == 'ru' || site == 'pt' || site == 'ja' || site == 'es') {
+                    site += '.stackoverflow.com';
+                } else if (site == 'rume' || site == 'ptme' || site == 'jame' || site == 'esme') {
+                    site = site.substring(0, 2) + '.meta.stackoverflow.com';
+                } else if (site.startsWith('meta.')) {
+                    site = site.substring(5) + '.meta.stackexchange.com';
+                } else {
+                    site += '.stackexchange.com';
+                }
+
+                // Fetch user ID
+                GM.xmlHttpRequest({
+                    method: 'GET',
+                    url: 'https://' + site + '/users/current',
+                    onload: function (data) {
+                        let matches = /\/users\/(\d+)\//g.exec(data.finalUrl);
+                        // Fill input field
+                        input.val(matches[1]);
+                    }
+                });
+                break;
+            }
+        }
+    });
+})();
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