The server detects too many rapid fragment requests and blocks further access.
yt-dlp --proxy http://PROXY_SERVER:PORT https://www.youtube.com/watch?v=VIDEO_ID yt-dlp http error 403: forbidden retrying fragment
HTTP Error 403: Forbidden is a status code returned by a web server when it understands the request but refuses to authorize it. In the context of yt-dlp , this error typically occurs when the YouTube algorithm detects and blocks the request from your IP address or the yt-dlp binary. The server detects too many rapid fragment requests
Some users reported success by disabling IPv6. You can do this by adding the --no-IPv6 flag: yt-dlp http error 403: forbidden retrying fragment
yt-dlp --user-agent <user_agent> <video_url>