diff --git a/yt_dlp/extractor/youtube.py b/yt_dlp/extractor/youtube.py
index e553fff9f..c97b784fa 100644
--- a/yt_dlp/extractor/youtube.py
+++ b/yt_dlp/extractor/youtube.py
@@ -1171,7 +1171,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         r'/(?P<id>[a-zA-Z0-9_-]{8,})/player(?:_ias\.vflset(?:/[a-zA-Z]{2,3}_[a-zA-Z]{2,3})?|-plasma-ias-(?:phone|tablet)-[a-z]{2}_[A-Z]{2}\.vflset)/base\.js$',
         r'\b(?P<id>vfl[a-zA-Z0-9_-]+)\b.*?\.js$',
     )
-    _formats = {
+    _formats = {  # NB: Used in YoutubeWebArchiveIE and GoogleDriveIE
         '5': {'ext': 'flv', 'width': 400, 'height': 240, 'acodec': 'mp3', 'abr': 64, 'vcodec': 'h263'},
         '6': {'ext': 'flv', 'width': 450, 'height': 270, 'acodec': 'mp3', 'abr': 64, 'vcodec': 'h263'},
         '13': {'ext': '3gp', 'acodec': 'aac', 'vcodec': 'mp4v'},