diff --git a/app.js b/app.js
index 7af1688..fb29486 100644
--- a/app.js
+++ b/app.js
@@ -170,7 +170,8 @@ global.syzoj = {
     app.use(Session(sessionConfig));
 
     app.use((req, res, next) => {
-      // req.session.user_id = 1;
+      res.locals.useLocalLibs = !!req.headers['syzoj-no-cdn'];
+
       let User = syzoj.model('user');
       if (req.session.user_id) {
         User.fromID(req.session.user_id).then((user) => {
@@ -181,7 +182,7 @@ global.syzoj = {
           res.locals.user = null;
           req.session.user_id = null;
           next();
-        })
+        });
       } else {
         if (req.cookies.login) {
           let obj;
diff --git a/views/header.ejs b/views/header.ejs
index be42227..c026729 100644
--- a/views/header.ejs
+++ b/views/header.ejs
@@ -12,7 +12,7 @@
     <link href="<%- lib('KaTeX/0.10.0/katex.min.css') %>" rel="stylesheet">
     <link href="<%- lib('morris.js/0.5.1/morris.css') %>" rel="stylesheet">
     <link href="/style.css?20181212" rel="stylesheet">
-    <% if (!syzoj.config.google_fonts_url) { %>
+    <% if (useLocalLibs || !syzoj.config.google_fonts_url) { %>
       <link href="<%- syzoj.utils.makeUrl(['google-fonts', 'fira-mono.css']) %>" rel="stylesheet">
       <link href="<%- syzoj.utils.makeUrl(['google-fonts', 'lato.css']) %>" rel="stylesheet">
       <link href="<%- syzoj.utils.makeUrl(['google-fonts', 'open-sans.css']) %>" rel="stylesheet">
diff --git a/views/util.ejs b/views/util.ejs
index 9e2bda1..d1cfe65 100644
--- a/views/util.ejs
+++ b/views/util.ejs
@@ -67,7 +67,7 @@ this.iconHidden = [
 ];
 
 this.lib = uri => {
-  if (!syzoj.config.cdnjs_url) {
+  if (useLocalLibs || !syzoj.config.cdnjs_url) {
     return syzoj.utils.makeUrl(['cdnjs', uri]);
   } else {
     return syzoj.config.cdnjs_url + '/' + uri;