diff --git a/output/styles2.css b/output/styles2.css
index 2ab3d3cf..9a271d67 100644
--- a/output/styles2.css
+++ b/output/styles2.css
@@ -80,6 +80,10 @@ html:not(.js) .js-only {
 	background-color: yellow;
 }
 
+.room-label-warning {
+	background-color: pink;
+}
+
 header {
 	display: flex;
 	direction: row;
diff --git a/php/utils/servers-rooms.php b/php/utils/servers-rooms.php
index 04b586e6..f79ac4a3 100644
--- a/php/utils/servers-rooms.php
+++ b/php/utils/servers-rooms.php
@@ -269,16 +269,31 @@
 		/**
 		 * @param string[] $tags
 		 */
-		function add_tags(array $tags) {
+		public function add_tags(array $tags) {
 			$this->tags = [...$this->tags, ...$tags];
 		}
 
+		private function has_nsfw_keywords(): bool {
+			// Description not included due to false positives.
+			$blob = 
+				strtolower($this->name) . " " .
+				strtolower(join(" ", $this->tags));
+
+			foreach (CommunityTag::NSFW_KEYWORDS as $keyword) {
+				if (str_contains($blob, $keyword)) {
+					return true;
+				}
+			}
+			
+			return false;
+		}
+
 		/**
 		 * Return the tags associated with this room.
 		 * @return \CommunityTag[] Tags as string array.
 		 */
 		function get_room_tags(): array {
-			$user_tags = CommunityTag::from_user_tags($this->tags);
+			$user_tags = CommunityTag::from_user_tags($this->tags, remove_redundant: true);
 
 			/**
 			 * @var \CommunityTag[] $derived_tags
@@ -289,6 +304,10 @@
 				$derived_tags[] = new CommunityTag("official", TagType::RESERVED_TAG);
 			}
 
+			if ($this->has_nsfw_keywords()) {
+				$derived_tags[] = new CommunityTag("nsfw", TagType::WARNING_TAG);
+			}
+
 			return [...$derived_tags, ...$user_tags];
 		}
 	}
diff --git a/php/utils/tags.php b/php/utils/tags.php
index 8ac34de4..b7ea3366 100644
--- a/php/utils/tags.php
+++ b/php/utils/tags.php
@@ -71,9 +71,12 @@
         /**
          * Returns the user tags given, without any reserved tags.
          * @param string[] $tags
+         * @param bool $remove_redundant Removes duplicate and obvious tags.
          * @return \CommunityTag[]
          */
-        public static function from_user_tags(array $tags): array {
+        public static function from_user_tags(
+            array $tags, bool $remove_redundant = false
+        ): array {
             $tags_user = array_filter(
 				$tags,
 				function($tag) {
@@ -81,7 +84,17 @@
 				}
 			);
 
-            return CommunityTag::from_tag_array($tags_user);
+            $tags_built = CommunityTag::from_tag_array($tags_user);
+
+            if ($remove_redundant) {
+                $tags_built = CommunityTag::dedupe_tags($tags_built);
+                $tags_built = array_filter($tags_built, function(\CommunityTag $tag) {
+                    $text = strtolower($tag->text);
+                    return !in_array($text, CommunityTag::REDUNDANT_TAGS);
+                });
+            }
+
+            return $tags_built;
         }
 
         /**
@@ -111,8 +124,12 @@
 		 * @var string[] RESERVED_TAGS
 		 * Array of derived tags unavailable for manual tagging.
 		 */
-		private const RESERVED_TAGS = ["official"];
+		private const RESERVED_TAGS = ["official", "nsfw"];
         
+        private const REDUNDANT_TAGS = ["session"];
+
+        public const NSFW_KEYWORDS = ["nsfw", "porn", "erotic", "18+"];
+
 		/**
 		 * Checks whether the given manual tag can be accepted.
 		 */