diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index d7a1586c0f..be1f3b0d77 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -2631,5 +2631,9 @@ def base_n(num, n, table):
     return ret
 
 
+def base36(num):
+    return base_n(num, 36, '0123456789abcdefghijklmnopqrstuvwxyz')
+
+
 def base62(num):
     return base_n(num, 62, '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')