diff --git a/libraries/osu_library.php b/libraries/osu_library.php
index 01b7f72..c5918e7 100644
--- a/libraries/osu_library.php
+++ b/libraries/osu_library.php
@@ -29,13 +29,21 @@ class osu_library
 		
 		$this->set_root($root); // update db entry
 		
-		$this->clear_library();
 		$glob = glob($this->get_library_folder() . "/*", GLOB_ONLYDIR);
 		
+		$library = $this->get_library();
 		natsort($glob); // i like wasting your processing power
 		foreach($glob as $folder)
 		{
-			$this->scan_add_folder($folder);
+			$key = basename($folder);
+			if (isset($library[$key]))
+			{
+				$this->scan_check_folder($folder);
+			}
+			else
+			{
+				$this->scan_add_folder($folder);
+			}
 		}
 		
 		$time_end = microtime(true);
@@ -54,6 +62,37 @@ class osu_library
 		unset($this->db["library"]);
 	}
 	
+	private function scan_check_folder(string $folder) : void
+	{
+		$key = basename($folder);
+		
+		$osu_glob = glob(utils::globsafe($folder) . "/*.osu");
+		$osb_glob = glob(utils::globsafe($folder) . "/*.osb");
+		$glob = array_merge($osu_glob, $osb_glob);
+		
+		$cacher = new osu_cacher($this->get_library_folder(), self::$cache_root);
+		
+		$changed = false;
+		if (count($osu_glob) < 1) 
+		{
+			$changed = true;
+		}
+		
+		foreach ($glob as $file)
+		{
+			if ($cacher->get_cache($file) === false)
+			{
+				$changed = true;
+			}
+		}
+		
+		if ($changed)
+		{
+			unset($this->db["library"][$key]);
+			$this->scan_add_folder($folder);
+		}
+	}
+	
 	private function scan_add_folder(string $folder) : void
 	{
 		$key = basename($folder);
diff --git a/libraries/osu_parser.php b/libraries/osu_parser.php
index 2641a3b..16e86b3 100644
--- a/libraries/osu_parser.php
+++ b/libraries/osu_parser.php
@@ -152,7 +152,7 @@ class osu_parser
 		unset($file); // remove the memory leak
 		
 		// storyboards are overloaded with dupes (renumber to make json export to arrays)
-		$parsed["storyboard"] = array_values(array_unique($parsed["storyboard"]));
+		if (!empty($parsed["storyboard"])) $parsed["storyboard"] = array_values(array_unique($parsed["storyboard"]));
 		
 		$time_end = microtime(true);
 		$parsing_time = $time_end - $time_start;
diff --git a/main.php b/main.php
index 8dd3581..f6ac867 100644
--- a/main.php
+++ b/main.php
@@ -27,6 +27,13 @@ function redirect($path)
 }
 
 if (isset($_GET["rescan"]))
+{
+	$lib->rescan_library(json_decode(file_get_contents("session/settings.json"), true)["osu_folder"]);
+	$lib->save_db();
+	redirect("./");
+}
+
+if (isset($_GET["scan"]))
 {
 	$lib->scan_library(json_decode(file_get_contents("session/settings.json"), true)["osu_folder"]);
 	$lib->save_db();
@@ -61,7 +68,8 @@ $start = file_get_contents("resources/start.html");
 $start = str_replace("{{ STYLE }}", file_get_contents("resources/style.css"), $start);
 echo $start;
 dump($lib, "lib");
-echo '<a href="./?rescan">[Rescan]</a> ';
+echo '<a href="./?scan">[Scan]</a> ';
+echo '<a href="./?rescan">[Force rescan]</a> ';
 echo '<a href="./?blacken">[Blacken]</a> ';
 echo '<a href="./?nosb">[NoSB]</a> ';
 echo '<a href="./?novid">[Novid]</a> ';