diff --git a/ui/pages/downloads.py b/ui/pages/downloads.py
index 51f9a777..2c04fcb6 100644
--- a/ui/pages/downloads.py
+++ b/ui/pages/downloads.py
@@ -7751,6 +7751,11 @@ class DownloadsPage(QWidget):
         sanitized = re.sub(r'[<>:"/\\|?*]', '_', filename)
         # Remove multiple spaces and trim
         sanitized = re.sub(r'\s+', ' ', sanitized).strip()
+        # Windows forbids trailing dots/spaces on files and folders
+        sanitized = sanitized.rstrip('. ') or '_'
+        # Windows reserved device names
+        if re.match(r'^(CON|PRN|AUX|NUL|COM[1-9]|LPT[1-9])(\.|$)', sanitized, re.IGNORECASE):
+            sanitized = '_' + sanitized
         # Limit length to avoid filesystem issues
         return sanitized[:200] if len(sanitized) > 200 else sanitized
     
diff --git a/web_server.py b/web_server.py
index 484f3cd5..6acf2097 100644
--- a/web_server.py
+++ b/web_server.py
@@ -12543,6 +12543,13 @@ def _sanitize_filename(filename: str) -> str:
     import re
     sanitized = re.sub(r'[<>:"/\\|?*]', '_', filename)
     sanitized = re.sub(r'\s+', ' ', sanitized).strip()
+    # Windows forbids trailing dots/spaces on files and folders.
+    # Artists like "Fred again.." would create mangled 8.3 short names.
+    sanitized = sanitized.rstrip('. ') or '_'
+    # Windows reserved device names (CON, PRN, AUX, NUL, COM1-9, LPT1-9)
+    # can't be used as file or folder names even with extensions.
+    if re.match(r'^(CON|PRN|AUX|NUL|COM[1-9]|LPT[1-9])(\.|$)', sanitized, re.IGNORECASE):
+        sanitized = '_' + sanitized
     return sanitized[:200]
 
 def _sanitize_context_values(context: dict) -> dict: