There are three ways to block online videos in WFilter 4.1：

1. Block video websites by url libiary in WFilter 4.1 .

Please refer to: How to block video websites

2. Block all video files. It only block videos playing and does not block websites.

Please refer to: How to block all video files

3. Block video protocols. You can block protocols in ‘Streaming’ to block video webiste and client.

Please refer to: How to block video streaming protocols?