diff --git a/docs/_theme/basicstrap/layout.html b/docs/_theme/basicstrap/layout.html
index d8c4ad83..362ed4d1 100644
--- a/docs/_theme/basicstrap/layout.html
+++ b/docs/_theme/basicstrap/layout.html
@@ -135,7 +135,9 @@
     {{ js_tag(scriptfile) }}
   {%- endif -%}
 {%- endfor %}
+{%- if theme_theme_preview|tobool %}
 <script type="text/javascript" src="{{ pathto('_static/js/jquery.cookie.min.js', 1) }}"></script>
+{%- endif %}
 <script type="text/javascript" src="{{ pathto('_static/js/basicstrap.js', 1) }}"></script>
 <script type="text/javascript">
   DOCUMENTATION_OPTIONS.FILE_SUFFIX = DOCUMENTATION_OPTIONS.FILE_SUFFIX || '.html';
diff --git a/docs/build-docs.py b/docs/build-docs.py
index 4f6fa93e..e2136afa 100644
--- a/docs/build-docs.py
+++ b/docs/build-docs.py
@@ -6,6 +6,35 @@ import subprocess
 import sys
 
 
+def prune_unused_local_assets(output_dir):
+    index_path = os.path.join(output_dir, "index.html")
+
+    try:
+        with open(index_path, "r", encoding="utf-8") as index_file:
+            index_html = index_file.read()
+    except OSError:
+        return
+
+    if "bootswatch-" not in index_html:
+        for bootstrap_version in ("bootstrap2", "bootstrap3"):
+            css_dir = os.path.join(
+                output_dir, "_static", "css", bootstrap_version
+            )
+            if not os.path.isdir(css_dir):
+                continue
+
+            for filename in os.listdir(css_dir):
+                if filename.startswith("bootswatch-") and filename.endswith(".css"):
+                    os.remove(os.path.join(css_dir, filename))
+
+    if "jquery.cookie.min.js" not in index_html:
+        js_dir = os.path.join(output_dir, "_static", "js")
+        for filename in ("jquery.cookie.min.js", "jquery.cookie-1.4.1.min.js"):
+            path = os.path.join(js_dir, filename)
+            if os.path.isfile(path):
+                os.remove(path)
+
+
 def main():
     if len(sys.argv) != 4:
         raise SystemExit("usage: build-docs.py SOURCE_DIR OUTPUT_DIR STAMP_FILE")
@@ -34,6 +63,8 @@ def main():
         check=True,
     )
 
+    prune_unused_local_assets(output_dir)
+
     with open(stamp_file, "w", encoding="utf-8") as stamp:
         stamp.write("built\n")