diff --git a/include/functions2.php b/include/functions2.php
index d06a7a71..b8eff56d 100644
--- a/include/functions2.php
+++ b/include/functions2.php
@@ -2428,7 +2428,10 @@
 	}
 
 	function theme_valid($theme) {
-		if ($theme == "default.php" || $theme == "night.css") return true; // needed for array_filter
+		$bundled_themes = [ "default.php", "night.css", "compact.css" ];
+		
+		if (in_array($theme, $bundled_themes)) return true;
+
 		$file = "themes/" . basename($theme);
 
 		if (!file_exists($file)) $file = "themes.local/" . basename($theme);
diff --git a/themes/compact.css b/themes/compact.css
new file mode 100644
index 00000000..51c3f7f9
--- /dev/null
+++ b/themes/compact.css
@@ -0,0 +1,19 @@
+/* supports-version:17.1 */
+
+@import "default.php";
+
+body,
+.claro .dijitMenu .dijitMenuItemLabel,
+.claro .cdmContentInner,
+.claro #content-insert,
+.claro .cdm .cdmContent,
+.claro .postReply .postContent { 
+	font-size : 12px ! important;
+}
+
+.claro .postReply .postHeader,
+.claro #floatingTitle a.title,
+.claro .cdm .title {
+	font-size : 13px ! important;
+}
+