diff --git a/copyparty/web/browser.js b/copyparty/web/browser.js
index 6de5bac7..66190b43 100644
--- a/copyparty/web/browser.js
+++ b/copyparty/web/browser.js
@@ -1052,7 +1052,7 @@ function goto(dest) {
 
 	clmod(document.documentElement, 'op_open', dest);
 
-	if (window['treectl'])
+	if (treectl)
 		treectl.onscroll();
 }
 
@@ -1508,7 +1508,7 @@ var widget = (function () {
 		clmod(document.documentElement, 'np_open', is_open);
 		clmod(widget, 'open', is_open);
 		bcfg_set('au_open', r.is_open = is_open);
-		if (window.vbar) {
+		if (vbar) {
 			pbar.onresize();
 			vbar.onresize();
 		}
@@ -2421,7 +2421,7 @@ function play(tid, is_ev, seek) {
 	clmod(ebi(oid), 'act', 1);
 	clmod(ebi(oid).closest('tr'), 'play', 1);
 	clmod(ebi('wtoggle'), 'np', mpl.clip);
-	if (window.thegrid)
+	if (thegrid)
 		thegrid.loadsel();
 
 	try {
@@ -3392,7 +3392,7 @@ var showfile = (function () {
 	}
 
 	r.setstyle = function () {
-		if (window['no_prism'])
+		if (window.no_prism)
 			return;
 
 		qsr('#prism_css');
@@ -3521,7 +3521,7 @@ var showfile = (function () {
 		else {
 			el.textContent = txt;
 			el.innerHTML = '<code>' + el.innerHTML + '</code>';
-			if (!window['no_prism']) {
+			if (!window.no_prism) {
 				el.className = 'prism linkable-line-numbers line-numbers language-' + lang;
 				if (!defer)
 					fun(el.firstChild);
@@ -3747,7 +3747,7 @@ var thegrid = (function () {
 		ebi('bdoc').style.display = 'none';
 		clmod(ebi('wrap'), 'doc');
 		qsr('#docname');
-		if (window['treectl'])
+		if (treectl)
 			treectl.textmode(false);
 
 		aligngriditems();
@@ -4610,7 +4610,7 @@ document.onkeydown = function (e) {
 })();
 
 function aligngriditems() {
-	if (!window.treectl)
+	if (!treectl)
 		return;
 
 	var em2px = parseFloat(getComputedStyle(ebi('ggrid')).fontSize);
@@ -5496,7 +5496,7 @@ function apply_perms(newperms) {
 				'table-cell' : 'none';
 	}
 
-	if (window['up2k'])
+	if (up2k)
 		up2k.set_fsearch();
 
 	ebi('widget').style.display = have_read ? '' : 'none';
@@ -5629,7 +5629,7 @@ var filecols = (function () {
 			for (var b = 0, bb = tds.length; b < bb; b++)
 				tds[b].className = cls;
 		}
-		if (window['tt']) {
+		if (tt) {
 			tt.att(ebi('hcols'));
 			tt.att(QS('#files>thead'));
 		}
@@ -6215,7 +6215,7 @@ function show_md(md, name, div, url, depth) {
 	if (url != now)
 		return;
 
-	if (!window['marked']) {
+	if (!marked) {
 		if (depth)
 			return toast.warn(10, errmsg + 'failed to load marked.js')
 
@@ -6579,7 +6579,7 @@ function reload_browser() {
 	for (var a = 0; a < ns.length; a++)
 		clmod(ebi(ns[a]), 'hidden', ebi('unsearch'));
 
-	if (window['up2k'])
+	if (up2k)
 		up2k.set_fsearch();
 
 	thegrid.setdirty();
diff --git a/copyparty/web/md.js b/copyparty/web/md.js
index 52adfb43..c0385d5e 100644
--- a/copyparty/web/md.js
+++ b/copyparty/web/md.js
@@ -498,5 +498,5 @@ dom_navtgl.onclick = function () {
 if (sread('hidenav') == 1)
     dom_navtgl.onclick();
 
-if (window['tt'])
+if (window.tt && tt.init)
     tt.init();
diff --git a/copyparty/web/up2k.js b/copyparty/web/up2k.js
index e1c528f0..ac4370cb 100644
--- a/copyparty/web/up2k.js
+++ b/copyparty/web/up2k.js
@@ -928,7 +928,7 @@ function up2k_init(subtle) {
     r.st = st;
     r.uc = uc;
 
-    if (!window.File || !File.prototype.slice || !window.FileReader || !window.FileList)
+    if (!window.File || !window.FileReader || !window.FileList || !File.prototype || !File.prototype.slice)
         return un2k(L.u_ever);
 
     var flag = false;
diff --git a/copyparty/web/util.js b/copyparty/web/util.js
index 4d6e6f64..906ffeeb 100644
--- a/copyparty/web/util.js
+++ b/copyparty/web/util.js
@@ -1,12 +1,13 @@
 "use strict";
 
-if (!window['console'])
-    window['console'] = {
+if (!window.console || !console.log)
+    window.console = {
         "log": function (msg) { }
     };
 
 
 var wah = '',
+    L, tt, treectl, thegrid, up2k, asmCrypto, hashwasm, vbar, marked,
     CB = '?_=' + Date.now(),
     HALFMAX = 8192 * 8192 * 8192 * 8192,
     HTTPS = (window.location + '').indexOf('https:') === 0,
@@ -17,6 +18,15 @@ var wah = '',
     IPHONE = TOUCH && /iPhone|iPad|iPod/i.test(navigator.userAgent),
     WINDOWS = navigator.platform ? navigator.platform == 'Win32' : /Windows/.test(navigator.userAgent);
 
+if (!window.WebAssembly || !WebAssembly.Memory)
+    window.WebAssembly = false;
+
+if (!window.Notification || !Notification.permission)
+    window.Notification = false;
+
+if (!window.FormData)
+    window.FormData = false;
+
 try {
     CB = '?' + document.currentScript.src.split('?').pop();
 
@@ -381,13 +391,14 @@ function clgot(el, cls) {
 
 
 var ANIM = true;
-if (window.matchMedia) {
+try {
     var mq = window.matchMedia('(prefers-reduced-motion: reduce)');
     mq.onchange = function () {
         ANIM = !mq.matches;
     };
     ANIM = !mq.matches;
 }
+catch (ex) { }
 
 
 function yscroll() {
@@ -747,7 +758,7 @@ function lhumantime(v) {
     var t = shumantime(v, 1),
         tp = t.replace(/([a-z])/g, " $1 ").split(/ /g).slice(0, -1);
 
-    if (!window.L || tp.length < 2 || tp[1].indexOf('$') + 1)
+    if (!L || tp.length < 2 || tp[1].indexOf('$') + 1)
         return t;
 
     var ret = '';
@@ -1251,8 +1262,8 @@ var modal = (function () {
         tok, tng, prim, sec, ok_cancel;
 
     r.load = function () {
-        tok = (window.L && L.m_ok) || 'OK';
-        tng = (window.L && L.m_ng) || 'Cancel';
+        tok = (L && L.m_ok) || 'OK';
+        tng = (L && L.m_ng) || 'Cancel';
         prim = '<a href="#" id="modal-ok">' + tok + '</a>';
         sec = '<a href="#" id="modal-ng">' + tng + '</a>';
         ok_cancel = WINDOWS ? prim + sec : sec + prim;
@@ -1612,7 +1623,7 @@ function xhrchk(xhr, prefix, e404, lvl, tag) {
         return true;
 
     if (xhr.status == 403)
-        return toast.err(0, prefix + (window.L && L.xhr403 || "403: access denied\n\ntry pressing F5, maybe you got logged out"), tag);
+        return toast.err(0, prefix + (L && L.xhr403 || "403: access denied\n\ntry pressing F5, maybe you got logged out"), tag);
 
     if (xhr.status == 404)
         return toast.err(0, prefix + e404, tag);