diff --git a/app/main.py b/app/main.py
index 7e1fefc..77e7ecf 100644
--- a/app/main.py
+++ b/app/main.py
@@ -33,17 +33,19 @@ class Config:
         'HOST': '0.0.0.0',
         'PORT': '8081',
         'BASE_DIR': '',
-        'DEFAULT_THEME': 'auto'
+        'DEFAULT_THEME': 'auto',
+        'DOWNLOAD_MODE': 'sequential',  # Can be 'sequential', 'concurrent', or 'limited'
+        'MAX_CONCURRENT_DOWNLOADS': 3,  # Used if DOWNLOAD_MODE is 'limited'
     }
 
     _BOOLEAN = ('DOWNLOAD_DIRS_INDEXABLE', 'CUSTOM_DIRS', 'CREATE_CUSTOM_DIRS', 'DELETE_FILE_ON_TRASHCAN')
 
     def __init__(self):
         for k, v in self._DEFAULTS.items():
-            setattr(self, k, os.environ[k] if k in os.environ else v)
+            setattr(self, k, os.environ.get(k, v))
 
         for k, v in self.__dict__.items():
-            if v.startswith('%%'):
+            if isinstance(v, str) and v.startswith('%%'):
                 setattr(self, k, getattr(self, v[2:]))
             if k in self._BOOLEAN:
                 if v not in ('true', 'false', 'True', 'False', 'on', 'off', '1', '0'):
@@ -160,9 +162,9 @@ async def start(request):
 async def history(request):
     history = { 'done': [], 'queue': []}
 
-    for _ ,v in dqueue.queue.saved_items():
+    for _, v in dqueue.queue.saved_items():
         history['queue'].append(v)
-    for _ ,v in dqueue.done.saved_items():
+    for _, v in dqueue.done.saved_items():
         history['done'].append(v)
 
     log.info("Sending download history")
diff --git a/app/ytdl.py b/app/ytdl.py
index 16133ec..b009257 100644
--- a/app/ytdl.py
+++ b/app/ytdl.py
@@ -216,6 +216,11 @@ class DownloadQueue:
         self.done = PersistentQueue(self.config.STATE_DIR + '/completed')
         self.pending = PersistentQueue(self.config.STATE_DIR + '/pending')
         self.active_downloads = set()
+        self.semaphore = None
+
+        if self.config.DOWNLOAD_MODE == 'limited':
+            self.semaphore = asyncio.Semaphore(self.config.MAX_CONCURRENT_DOWNLOADS)
+        
         self.done.load()
 
     async def __import_queue(self):
@@ -226,6 +231,49 @@ class DownloadQueue:
         log.info("Initializing DownloadQueue")
         asyncio.create_task(self.__import_queue())
 
+    async def __start_download(self, download):
+        if self.config.DOWNLOAD_MODE == 'sequential':
+            await self.__sequential_download(download)
+        elif self.config.DOWNLOAD_MODE == 'limited' and self.semaphore is not None:
+            await self.__limited_concurrent_download(download)
+        else:  # concurrent without limit
+            await self.__concurrent_download(download)
+
+    async def __sequential_download(self, download):
+        log.info("Starting sequential download.")
+        await download.start(self.notifier)
+        self._post_download_cleanup(download)
+
+    async def __concurrent_download(self, download):
+        log.info("Starting concurrent download without limits.")
+        asyncio.create_task(self._run_download(download))
+
+    async def __limited_concurrent_download(self, download):
+        log.info("Starting limited concurrent download.")
+        async with self.semaphore:
+            await self._run_download(download)
+
+    async def _run_download(self, download):
+        await download.start(self.notifier)
+        self._post_download_cleanup(download)
+
+    def _post_download_cleanup(self, download):
+        if download.info.status != 'finished':
+            if download.tmpfilename and os.path.isfile(download.tmpfilename):
+                try:
+                    os.remove(download.tmpfilename)
+                except:
+                    pass
+            download.info.status = 'error'
+        download.close()
+        if self.queue.exists(download.info.url):
+            self.queue.delete(download.info.url)
+            if download.canceled:
+                asyncio.create_task(self.notifier.canceled(download.info.url))
+            else:
+                self.done.put(download)
+                asyncio.create_task(self.notifier.completed(download.info))
+
     def __extract_info(self, url):
         return yt_dlp.YoutubeDL(params={
             'quiet': True,
@@ -304,24 +352,6 @@ class DownloadQueue:
             return await self.add(entry['url'], quality, format, folder, custom_name_prefix, auto_start, already)
         return {'status': 'error', 'msg': f'Unsupported resource "{etype}"'}
 
-    async def __start_download(self, download):
-        await download.start(self.notifier)
-        if download.info.status != 'finished':
-            if download.tmpfilename and os.path.isfile(download.tmpfilename):
-                try:
-                    os.remove(download.tmpfilename)
-                except:
-                    pass
-            download.info.status = 'error'
-        download.close()
-        if self.queue.exists(download.info.url):
-            self.queue.delete(download.info.url)
-            if download.canceled:
-                await self.notifier.canceled(download.info.url)
-            else:
-                self.done.put(download)
-                await self.notifier.completed(download.info)
-
     async def add(self, url, quality, format, folder, custom_name_prefix, auto_start=True, already=None):
         log.info(f'adding {url}: {quality=} {format=} {already=} {folder=} {custom_name_prefix=}')
         already = set() if already is None else already