diff --git a/_config.yml b/_config.yml
index 5ec03f156a..4d0ddcb140 100644
--- a/_config.yml
+++ b/_config.yml
@@ -506,7 +506,7 @@ font:
 #   - CDNJS (cdnjs.cloudflare.com), provided by cloudflare
 # ---------------------------------------------------------------
 
-# Math Equations Render Support
+# Math Formulas Render Support
 math:
   enable: false
 
@@ -515,28 +515,17 @@ math:
   # If you set it to false, it will load mathjax / katex srcipt EVERY PAGE.
   per_page: true
 
-  engine: mathjax
-  #engine: katex
-
   # hexo-renderer-pandoc (or hexo-renderer-kramed) required for full MathJax support.
   mathjax:
-    cdn: //cdn.jsdelivr.net/npm/mathjax@2/MathJax.js?config=TeX-AMS-MML_HTMLorMML
-    #cdn: //cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-MML-AM_CHTML
-
+    enable: false
     # See: https://mhchem.github.io/MathJax-mhchem/
-    #mhchem: //cdn.jsdelivr.net/npm/mathjax-mhchem@3
-    #mhchem: //cdnjs.cloudflare.com/ajax/libs/mathjax-mhchem/3.3.0
+    mhchem: false
 
   # hexo-renderer-markdown-it-plus (or hexo-renderer-markdown-it with markdown-it-katex plugin) required for full Katex support.
   katex:
-    cdn: //cdn.jsdelivr.net/npm/katex@0/dist/katex.min.css
-    #cdn: //cdnjs.cloudflare.com/ajax/libs/KaTeX/0.7.1/katex.min.css
-
-    copy_tex:
-      # See: https://github.com/KaTeX/KaTeX/tree/master/contrib/copy-tex
-      enable: false
-      copy_tex_js: //cdn.jsdelivr.net/npm/katex@0/dist/contrib/copy-tex.min.js
-      copy_tex_css: //cdn.jsdelivr.net/npm/katex@0/dist/contrib/copy-tex.min.css
+    enable: false
+    # See: https://github.com/KaTeX/KaTeX/tree/master/contrib/copy-tex
+    copy_tex: false
 
 # Easily enable fast Ajax navigation on your website.
 # Dependencies: https://github.com/theme-next/theme-next-pjax
@@ -936,17 +925,12 @@ pdf:
   enable: false
   # Default height
   height: 500px
-  pdfobject:
-    cdn: //cdn.jsdelivr.net/npm/pdfobject@2/pdfobject.min.js
-    #cdn: //cdnjs.cloudflare.com/ajax/libs/pdfobject/2.1.1/pdfobject.min.js
 
 # Mermaid tag
 mermaid:
   enable: false
   # Available themes: default | dark | forest | neutral
   theme: forest
-  cdn: //cdn.jsdelivr.net/npm/mermaid@8/dist/mermaid.min.js
-  #cdn: //cdnjs.cloudflare.com/ajax/libs/mermaid/8.0.0/mermaid.min.js
 
 
 # ---------------------------------------------------------------
@@ -1038,6 +1022,25 @@ vendors:
   # fontawesome: //cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css
   fontawesome:
 
+  # MathJax
+  # Example:
+  # mathjax: //cdn.jsdelivr.net/npm/mathjax@2/MathJax.js?config=TeX-AMS-MML_HTMLorMML
+  # mathjax: //cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-MML-AM_CHTML
+  # mhchem: //cdn.jsdelivr.net/npm/mathjax-mhchem@3
+  # mhchem: //cdnjs.cloudflare.com/ajax/libs/mathjax-mhchem/3.3.0
+  mathjax:
+  mhchem:
+
+  # KaTeX
+  # Example:
+  # katex: //cdn.jsdelivr.net/npm/katex@0/dist/katex.min.css
+  # katex: //cdnjs.cloudflare.com/ajax/libs/KaTeX/0.7.1/katex.min.css
+  # copy_tex_js: //cdn.jsdelivr.net/npm/katex@0/dist/contrib/copy-tex.min.js
+  # copy_tex_css: //cdn.jsdelivr.net/npm/katex@0/dist/contrib/copy-tex.min.css
+  katex:
+  copy_tex_js:
+  copy_tex_css:
+
   # Internal version: 0.2.8
   # Example:
   # pjax: //cdn.jsdelivr.net/gh/theme-next/theme-next-pjax@0/pjax.min.js
@@ -1125,6 +1128,18 @@ vendors:
   algolia_instant_js:
   algolia_instant_css:
 
+  # PDF
+  # Example:
+  # pdfobject: //cdn.jsdelivr.net/npm/pdfobject@2/pdfobject.min.js
+  # pdfobject: //cdnjs.cloudflare.com/ajax/libs/pdfobject/2.1.1/pdfobject.min.js
+  pdfobject:
+
+  # Mermaid
+  # Example:
+  # mermaid: //cdn.jsdelivr.net/npm/mermaid@8/dist/mermaid.min.js
+  # mermaid: //cdnjs.cloudflare.com/ajax/libs/mermaid/8.0.0/mermaid.min.js
+  mermaid:
+
   # Internal version: 1.2.1
   # Example:
   # velocity: //cdn.jsdelivr.net/npm/velocity-animate@1/velocity.min.js
diff --git a/layout/_partials/head/head.swig b/layout/_partials/head/head.swig
index c483920608..7e233adc25 100644
--- a/layout/_partials/head/head.swig
+++ b/layout/_partials/head/head.swig
@@ -49,47 +49,29 @@
 
 {{ next_font() }}
 
-{%- set font_awesome_uri = url_for(theme.vendors._internal + '/font-awesome/css/font-awesome.min.css?v=4.7.0') %}
-{%- if theme.vendors.fontawesome %}
-  {%- set font_awesome_uri = theme.vendors.fontawesome %}
-{%- endif %}
+{%- set font_awesome_uri = theme.vendors.fontawesome | default(url_for(theme.vendors._internal + '/font-awesome/css/font-awesome.min.css?v=4.7.0')) %}
 <link rel="stylesheet" href="{{ font_awesome_uri }}">
 
 {%- if theme.fancybox %}
-  {%- set fancybox_css_uri = url_for(theme.vendors._internal + '/fancybox/source/jquery.fancybox.css') %}
-  {%- if theme.vendors.fancybox_css %}
-    {%- set fancybox_css_uri = theme.vendors.fancybox_css %}
-  {%- endif %}
+  {%- set fancybox_css_uri = theme.vendors.fancybox_css | default(url_for(theme.vendors._internal + '/fancybox/source/jquery.fancybox.css')) %}
   <link rel="stylesheet" href="{{ fancybox_css_uri }}">
 {%- endif %}
 
 {%- if theme.likely.enable %}
-  {%- set likely_css_url = '//cdn.jsdelivr.net/npm/ilyabirman-likely@2/release/likely.css' %}
-  {%- if theme.vendors.likely_css %}
-    {%- set likely_css_url = theme.vendors.likely_css %}
-  {%- endif %}
-  <link rel="stylesheet" href="{{ likely_css_url }}">
+  {%- set likely_css_uri = theme.vendors.likely_css | default('//cdn.jsdelivr.net/npm/ilyabirman-likely@2/release/likely.css') %}
+  <link rel="stylesheet" href="{{ likely_css_uri }}">
 {%- endif %}
 
 {%- if theme.needmoreshare2.enable %}
-  {%- set needmoreshare2_css = url_for(theme.vendors._internal + '/needsharebutton/needsharebutton.css') %}
-  {%- if theme.vendors.needmoreshare2_css %}
-    {%- set needmoreshare2_css = theme.vendors.needmoreshare2_css %}
-  {%- endif %}
-  <link rel="stylesheet" href="{{ needmoreshare2_css }}">
+  {%- set needmoreshare2_css_uri = theme.vendors.needmoreshare2_css | default(url_for(theme.vendors._internal + '/needsharebutton/needsharebutton.css')) %}
+  <link rel="stylesheet" href="{{ needmoreshare2_css_uri }}">
 {%- endif %}
 
 {%- if theme.pace.enable %}
-  {%- set pace_css_uri = url_for(theme.vendors._internal + '/pace/pace-theme-'+ theme.pace.theme +'.min.css?v=1.0.2') %}
-  {%- set pace_js_uri = url_for(theme.vendors._internal + '/pace/pace.min.js?v=1.0.2') %}
-    {%- if theme.vendors.pace %}
-      {%- set pace_js_uri = theme.vendors.pace %}
-    {%- endif %}
-    {%- if theme.vendors.pace_css %}
-      {%- set pace_css_uri = theme.vendors.pace_css %}
-    {%- endif %}
-  <script src="{{ pace_js_uri }}"></script>
+  {%- set pace_css_uri = theme.vendors.pace_css | default(url_for(theme.vendors._internal + '/pace/pace-theme-' + theme.pace.theme + '.min.css?v=1.0.2')) %}
+  {%- set pace_js_uri = theme.vendors.pace | default(url_for(theme.vendors._internal + '/pace/pace.min.js?v=1.0.2')) %}
   <link rel="stylesheet" href="{{ pace_css_uri }}">
+  <script src="{{ pace_js_uri }}"></script>
 {%- endif %}
 
 {# Export some HEXO Configurations to Front-End #}
diff --git a/layout/_partials/share/likely.swig b/layout/_partials/share/likely.swig
index 5e7a3ca893..42b40f1142 100644
--- a/layout/_partials/share/likely.swig
+++ b/layout/_partials/share/likely.swig
@@ -1,5 +1,2 @@
-{%- set likely_js_url = '//cdn.jsdelivr.net/npm/ilyabirman-likely@2/release/likely.js' %}
-{%- if theme.vendors.likely_js %}
-  {%- set likely_js_url = theme.vendors.likely_js %}
-{%- endif %}
-<script src="{{ likely_js_url }}"></script>
+{%- set likely_js_uri = theme.vendors.likely_js | default('//cdn.jsdelivr.net/npm/ilyabirman-likely@2/release/likely.js') %}
+<script src="{{ likely_js_uri }}"></script>
diff --git a/layout/_partials/share/needsharebutton.swig b/layout/_partials/share/needsharebutton.swig
index 8b4075c4d7..a183a69f52 100644
--- a/layout/_partials/share/needsharebutton.swig
+++ b/layout/_partials/share/needsharebutton.swig
@@ -6,11 +6,8 @@
   </div>
 {%- endif %}
 
-{%- set needmoreshare2_js = url_for(theme.vendors._internal + '/needsharebutton/needsharebutton.js') %}
-{%- if theme.vendors.needmoreshare2_js %}
-  {%- set needmoreshare2_js = theme.vendors.needmoreshare2_js %}
-{%- endif %}
-<script src="{{ needmoreshare2_js }}"></script>
+{%- set needmoreshare2_js_uri = theme.vendors.needmoreshare2_js | default(url_for(theme.vendors._internal + '/needsharebutton/needsharebutton.js')) %}
+<script src="{{ needmoreshare2_js_uri }}"></script>
 <script>
   {%- if theme.needmoreshare2.postbottom.enable %}
     pbOptions = {};
diff --git a/layout/_scripts/three.swig b/layout/_scripts/three.swig
index 78d1415661..bb3d20656d 100644
--- a/layout/_scripts/three.swig
+++ b/layout/_scripts/three.swig
@@ -1,29 +1,26 @@
 {%- if theme.three.enable and theme.three.delay %}
-  {%- set three_url = url_for(theme.vendors._internal + '/three/three.min.js') %}
-  {%- if theme.vendors.three %}
-    {%- set three_url = theme.vendors.three %}
-  {%- endif %}
+  {%- set three_uri = theme.vendors.three | default(url_for(theme.vendors._internal + '/three/three.min.js')) %}
 
   {%- if theme.three.three_waves %}
-    {%- set waves = theme.vendors.three_waves | default(url_for(theme.vendors._internal + '/three/three-waves.min.js')) %}
+    {%- set waves_uri = theme.vendors.three_waves | default(url_for(theme.vendors._internal + '/three/three-waves.min.js')) %}
   {%- endif %}
 
   {%- if theme.three.canvas_lines %}
-    {%- set lines = theme.vendors.canvas_lines | default(url_for(theme.vendors._internal + '/three/canvas_lines.min.js')) %}
+    {%- set lines_uri = theme.vendors.canvas_lines | default(url_for(theme.vendors._internal + '/three/canvas_lines.min.js')) %}
   {%- endif %}
 
   {%- if theme.three.canvas_sphere %}
-    {%- set sphere = theme.vendors.canvas_sphere | default(url_for(theme.vendors._internal + '/three/canvas_sphere.min.js')) %}
+    {%- set sphere_uri = theme.vendors.canvas_sphere | default(url_for(theme.vendors._internal + '/three/canvas_sphere.min.js')) %}
   {%- endif %}
 
   <script>
     ;((d, w) => {
       loadThree = () => {
         let s = d.createElement('script');
-        s.src = '{{ three_url }}';
+        s.src = '{{ three_uri }}';
         d.body.appendChild(s);
       }
-      let styles = ['{{ waves }}', '{{ lines }}', '{{ sphere }}'];
+      let styles = ['{{ waves_uri }}', '{{ lines_uri }}', '{{ sphere_uri }}'];
       loadStyle = () => {
         styles.forEach(x => {
           if (x !== '') {
diff --git a/layout/_scripts/vendors.swig b/layout/_scripts/vendors.swig
index 896f0ca21c..f3273e1ef0 100644
--- a/layout/_scripts/vendors.swig
+++ b/layout/_scripts/vendors.swig
@@ -48,24 +48,15 @@
 
 {%- if theme.canvas_nest.enable %}
   {%- if theme.canvas_nest.onmobile %}
-    {%- set canvas_nest_uri = url_for(theme.vendors._internal + '/canvas-nest/canvas-nest.min.js') %}
-    {%- if theme.vendors.canvas_nest %}
-      {%- set canvas_nest_uri = theme.vendors.canvas_nest %}
-    {%- endif %}
+    {%- set canvas_nest_uri = theme.vendors.canvas_nest | default(url_for(theme.vendors._internal + '/canvas-nest/canvas-nest.min.js')) %}
   {% else %}
-    {%- set canvas_nest_uri = url_for(theme.vendors._internal + '/canvas-nest/canvas-nest-nomobile.min.js') %}
-    {%- if theme.vendors.canvas_nest_nomobile %}
-      {%- set canvas_nest_uri = theme.vendors.canvas_nest_nomobile %}
-    {%- endif %}
+    {%- set canvas_nest_uri = theme.vendors.canvas_nest_nomobile | default(url_for(theme.vendors._internal + '/canvas-nest/canvas-nest-nomobile.min.js')) %}
   {%- endif %}
   <script color='{{ theme.canvas_nest.color }}' opacity='{{ theme.canvas_nest.opacity }}' zIndex='{{ theme.canvas_nest.zIndex }}' count='{{ theme.canvas_nest.count }}' src="{{ canvas_nest_uri }}"></script>
 {%- endif %}
 
 {%- if theme.canvas_ribbon.enable %}
-  {%- set canvas_ribbon_uri = url_for(theme.vendors._internal + '/canvas-ribbon/canvas-ribbon.js') %}
-  {%- if theme.vendors.canvas_ribbon %}
-    {%- set canvas_ribbon_uri = theme.vendors.canvas_ribbon %}
-  {%- endif %}
+  {%- set canvas_ribbon_uri = theme.vendors.canvas_ribbon | default(url_for(theme.vendors._internal + '/canvas-ribbon/canvas-ribbon.js')) %}
   <script size="{{ theme.canvas_ribbon.size }}" alpha="{{ theme.canvas_ribbon.alpha }}" zIndex="{{theme.canvas_ribbon.zIndex }}" src="{{ canvas_ribbon_uri }}"></script>
 {%- endif %}
 
diff --git a/layout/_third-party/bookmark.swig b/layout/_third-party/bookmark.swig
index 332e49e1ba..655e923a80 100644
--- a/layout/_third-party/bookmark.swig
+++ b/layout/_third-party/bookmark.swig
@@ -1,8 +1,5 @@
 {%- if theme.bookmark.enable %}
-  {%- set bookmark_uri = url_for(theme.vendors._internal + '/bookmark/bookmark.min.js?v=1.0') %}
-  {%- if theme.vendors.bookmark %}
-    {%- set bookmark_uri = theme.vendors.bookmark %}
-  {%- endif %}
+  {%- set bookmark_uri = theme.vendors.bookmark | default(url_for(theme.vendors._internal + '/bookmark/bookmark.min.js?v=1.0')) %}
   <script src="{{ bookmark_uri }}"></script>
   <script{{ pjax }}>
   if (CONFIG.page.isPost) {
diff --git a/layout/_third-party/comments/disqusjs.swig b/layout/_third-party/comments/disqusjs.swig
index df0bbb6e7b..02d3b5f64b 100644
--- a/layout/_third-party/comments/disqusjs.swig
+++ b/layout/_third-party/comments/disqusjs.swig
@@ -1,17 +1,11 @@
 {%- if page.comments %}
-{%- set disqusjs_css_url = '//cdn.jsdelivr.net/npm/disqusjs@1/dist/disqusjs.css' %}
-{%- if theme.vendors.disqusjs_css %}
-  {%- set disqusjs_css_url = theme.vendors.disqusjs_css %}
-{%- endif %}
-<link rel="stylesheet" href="{{ disqusjs_css_url }}">
+{%- set disqusjs_css_uri = theme.vendors.disqusjs_css | default('//cdn.jsdelivr.net/npm/disqusjs@1/dist/disqusjs.css') %}
+<link rel="stylesheet" href="{{ disqusjs_css_uri }}">
 
-{%- set disqusjs_js_url = '//cdn.jsdelivr.net/npm/disqusjs@1/dist/disqus.js' %}
-{%- if theme.vendors.disqusjs_js %}
-  {%- set disqusjs_js_url = theme.vendors.disqusjs_js %}
-{%- endif %}
+{%- set disqusjs_js_uri = theme.vendors.disqusjs_js | default('//cdn.jsdelivr.net/npm/disqusjs@1/dist/disqus.js') %}
 
 <script>
-  NexT.utils.getScript('{{ disqusjs_js_url }}', function() {
+  NexT.utils.getScript('{{ disqusjs_js_uri }}', function() {
     window.dsqjs = new DisqusJS({
       api: '{{ theme.disqusjs.api }}' || 'https://disqus.com/api/',
       apikey: '{{ theme.disqusjs.apikey }}',
diff --git a/layout/_third-party/comments/gitalk.swig b/layout/_third-party/comments/gitalk.swig
index 5992a03798..a82205fac4 100644
--- a/layout/_third-party/comments/gitalk.swig
+++ b/layout/_third-party/comments/gitalk.swig
@@ -1,17 +1,11 @@
 {%- if page.comments %}
-{%- set gitalk_css_url = '//cdn.jsdelivr.net/npm/gitalk@1/dist/gitalk.min.css' %}
-{%- if theme.vendors.gitalk_css %}
-  {%- set gitalk_css_url = theme.vendors.gitalk_css %}
-{%- endif %}
-<link rel="stylesheet" href="{{ gitalk_css_url }}">
+{%- set gitalk_css_uri = theme.vendors.gitalk_css | default('//cdn.jsdelivr.net/npm/gitalk@1/dist/gitalk.min.css') %}
+<link rel="stylesheet" href="{{ gitalk_css_uri }}">
 
-{%- set gitalk_js_url = '//cdn.jsdelivr.net/npm/gitalk@1/dist/gitalk.min.js' %}
-{%- if theme.vendors.gitalk_js %}
-  {%- set gitalk_js_url = theme.vendors.gitalk_js %}
-{%- endif %}
+{%- set gitalk_js_uri = theme.vendors.gitalk_js | default('//cdn.jsdelivr.net/npm/gitalk@1/dist/gitalk.min.js') %}
 
 <script>
-  NexT.utils.getScript('{{ gitalk_js_url }}', function() {
+  NexT.utils.getScript('{{ gitalk_js_uri }}', function() {
     var gitalk = new Gitalk({
       clientID: '{{ theme.gitalk.client_id }}',
       clientSecret: '{{ theme.gitalk.client_secret }}',
diff --git a/layout/_third-party/comments/valine.swig b/layout/_third-party/comments/valine.swig
index 274ac0fb40..0868158f64 100644
--- a/layout/_third-party/comments/valine.swig
+++ b/layout/_third-party/comments/valine.swig
@@ -1,7 +1,4 @@
-{%- set valine_uri = '//unpkg.com/valine/dist/Valine.min.js' %}
-{%- if theme.vendors.valine %}
-  {%- set valine_uri = theme.vendors.valine %}
-{%- endif %}
+{%- set valine_uri = theme.vendors.valine | default('//unpkg.com/valine/dist/Valine.min.js') %}
 
 <script>
 NexT.utils.getScript('{{ valine_uri }}', function() {
diff --git a/layout/_third-party/math/index.swig b/layout/_third-party/math/index.swig
index b62ed75035..d4082203cd 100644
--- a/layout/_third-party/math/index.swig
+++ b/layout/_third-party/math/index.swig
@@ -11,9 +11,9 @@
   {%- endif %}
 
   {%- if not theme.math.per_page or is_index_has_math or page.mathjax %}
-    {%- if theme.math.engine == 'mathjax' %}
+    {%- if theme.math.mathjax.enable %}
       {% include 'mathjax.swig' %}
-    {% elif theme.math.engine == 'katex' %}
+    {% elif theme.math.katex.enable %}
       {% include 'katex.swig' %}
     {%- endif %}
   {%- endif %}
diff --git a/layout/_third-party/math/katex.swig b/layout/_third-party/math/katex.swig
index a0ec731d19..30f62b91a8 100644
--- a/layout/_third-party/math/katex.swig
+++ b/layout/_third-party/math/katex.swig
@@ -1,9 +1,8 @@
-<link rel="stylesheet" href="{{ theme.math.katex.cdn }}">
-{%- if theme.math.katex.copy_tex.enable %}
-  {%- if theme.math.katex.copy_tex.copy_tex_js %}
-    <script src="{{ theme.math.katex.copy_tex.copy_tex_js }}"></script>
-  {%- endif %}
-  {%- if theme.math.katex.copy_tex.copy_tex_css %}
-    <link rel="stylesheet" href="{{ theme.math.katex.copy_tex.copy_tex_css }}">
-  {%- endif %}
+{%- set katex_uri = theme.vendors.katex | default('//cdn.jsdelivr.net/npm/katex@0/dist/contrib/copy-tex.min.js') %}
+<link rel="stylesheet" href="{{ katex_uri }}">
+{%- if theme.math.katex.copy_tex %}
+  {%- set copy_tex_js_uri = theme.vendors.copy_tex_js | default('//cdn.jsdelivr.net/npm/katex@0/dist/contrib/copy-tex.min.js') %}
+  {%- set copy_tex_css_uri = theme.vendors.copy_tex_css | default('//cdn.jsdelivr.net/npm/katex@0/dist/contrib/copy-tex.min.css') %}
+  <script src="{{ copy_tex_js_uri }}"></script>
+  <link rel="stylesheet" href="{{ copy_tex_css_uri }}">
 {%- endif %}
diff --git a/layout/_third-party/math/mathjax.swig b/layout/_third-party/math/mathjax.swig
index 11d16abf7c..c7f9b915f4 100644
--- a/layout/_third-party/math/mathjax.swig
+++ b/layout/_third-party/math/mathjax.swig
@@ -1,6 +1,7 @@
+{%- set mhchem_uri = theme.vendors.mhchem | default('//cdn.jsdelivr.net/npm/mathjax-mhchem@3') %}
 <script type="text/x-mathjax-config">
   {%- if theme.math.mathjax.mhchem %}
-    MathJax.Ajax.config.path['mhchem'] = '{{ theme.math.mathjax.mhchem }}';
+    MathJax.Ajax.config.path['mhchem'] = '{{ mhchem_uri }}';
   {%- endif %}
 
   MathJax.Hub.Config({
@@ -44,8 +45,9 @@
     }
   });
 </script>
+{%- set mathjax_uri = theme.vendors.mathjax | default('//cdn.jsdelivr.net/npm/mathjax@2/MathJax.js?config=TeX-AMS-MML_HTMLorMML') %}
 <script>
-  NexT.utils.getScript('{{ theme.math.mathjax.cdn }}', function() {
+  NexT.utils.getScript('{{ mathjax_uri }}', function() {
     MathJax.Hub.Typeset();
   }, window.MathJax);
 </script>
diff --git a/layout/_third-party/quicklink.swig b/layout/_third-party/quicklink.swig
index c94f474d07..4c02a3090d 100644
--- a/layout/_third-party/quicklink.swig
+++ b/layout/_third-party/quicklink.swig
@@ -1,8 +1,5 @@
 {%- if theme.quicklink.enable %}
-  {%- set quicklink_uri = url_for(theme.vendors._internal + '/quicklink/quicklink.umd.js') %}
-  {%- if theme.vendors.quicklink %}
-    {%- set quicklink_uri = theme.vendors.quicklink %}
-  {%- endif %}
+  {%- set quicklink_uri = theme.vendors.quicklink | default(url_for(theme.vendors._internal + '/quicklink/quicklink.umd.js')) %}
 
   {%- if is_home() %}
     {%- if theme.quicklink.home %}
diff --git a/layout/_third-party/search/algolia-search.swig b/layout/_third-party/search/algolia-search.swig
index d1a46b4368..6f0feb89ea 100644
--- a/layout/_third-party/search/algolia-search.swig
+++ b/layout/_third-party/search/algolia-search.swig
@@ -1,15 +1,6 @@
-{# S: Include Algolia instantsearch.js library #}
-{%- set algolia_instant_css = url_for(theme.vendors._internal + '/algolia-instant-search/instantsearch.min.css') %}
-{%- if theme.vendors.algolia_instant_css %}
-  {%- set algolia_instant_css = theme.vendors.algolia_instant_css %}
-{%- endif %}
-<link rel="stylesheet" href="{{ algolia_instant_css }}">
-
-{%- set algolia_instant_js = url_for(theme.vendors._internal + '/algolia-instant-search/instantsearch.min.js') %}
-{%- if theme.vendors.algolia_instant_js %}
-  {%- set algolia_instant_js = theme.vendors.algolia_instant_js %}
-{%- endif %}
-<script src="{{ algolia_instant_js }}"></script>
-{# E: Include Algolia instantsearch.js library #}
+{%- set algolia_instant_css_uri = theme.vendors.algolia_instant_css | default(url_for(theme.vendors._internal + '/algolia-instant-search/instantsearch.min.css')) %}
+{%- set algolia_instant_js_uri = theme.vendors.algolia_instant_js | default(url_for(theme.vendors._internal + '/algolia-instant-search/instantsearch.min.js')) %}
+<link rel="stylesheet" href="{{ algolia_instant_css_uri }}">
+<script src="{{ algolia_instant_js_uri }}"></script>
 
 <script src="{{ url_for(theme.js) }}/algolia-search.js?v={{ version }}"></script>
diff --git a/layout/_third-party/tags/mermaid.swig b/layout/_third-party/tags/mermaid.swig
index c2933658e2..4f6b43bebc 100644
--- a/layout/_third-party/tags/mermaid.swig
+++ b/layout/_third-party/tags/mermaid.swig
@@ -1,7 +1,8 @@
 {%- if theme.mermaid.enable %}
+{%- set mermaid_uri = theme.vendors.mermaid | default('//cdn.jsdelivr.net/npm/mermaid@8/dist/mermaid.min.js') %}
 <script{{ pjax }}>
 if ($('body').find('pre.mermaid').length) {
-  NexT.utils.getScript('{{ theme.mermaid.cdn }}', function() {
+  NexT.utils.getScript('{{ mermaid_uri }}', function() {
     mermaid.initialize({
       theme: '{{ theme.mermaid.theme }}',
       logLevel: 3,
diff --git a/layout/_third-party/tags/pdf.swig b/layout/_third-party/tags/pdf.swig
index fdb465faa3..46f5a6638d 100644
--- a/layout/_third-party/tags/pdf.swig
+++ b/layout/_third-party/tags/pdf.swig
@@ -1,7 +1,8 @@
 {%- if theme.pdf.enable %}
+{%- set pdfobject_uri = theme.vendors.pdfobject | default('//cdn.jsdelivr.net/npm/pdfobject@2/pdfobject.min.js') %}
 <script{{ pjax }}>
 if ($('body').find('div.pdf').length) {
-  NexT.utils.getScript('{{ theme.pdf.pdfobject.cdn }}', function() {
+  NexT.utils.getScript('{{ pdfobject_uri }}', function() {
     $('body').find('div.pdf').each(function(i, o) {
       PDFObject.embed($(o).attr('target'), $(o), {
         pdfOpenParams: {